Any time you’re working on a mix that’s going to broadcast, it’s important to ask for specs. Specs are essentially a set of rules for each broadcaster, such as:
- How loud content can be (overall average and peak levels)
- What format to deliver (files – including file type and bit depth; or tape)
- Specific mix requirements (such as “no music in the center channel”)
My understanding of the -24LKFS standard was that I could avoid too much hard limiting and compression and aim for the best sounding mix inside the guidelines. Any tips to get the nest cut through using the new standards? Any help much appreciated. 224LKFSChannelCheckLFE.wav -inf LKFS -inf LKFS Left channel gain check. 100 Hz @ −23 and 1 kHz sine wave @ −24 dBFS in LFE channel. If LFE included with full bandwidth with channel weighting of.
- Ffprobe options inputurl 2 Description. Ffprobe gathers information from multimedia streams and prints it in human- and machine-readable fashion. For example it can be used to check the format of the container used by a multimedia stream and the format and type of each media stream contained in it.
- Atmos mixes must adhere to the LKFS spec of -24LKFS. Atmos mixes do not need to adhere to True Peak spec of -2dBFS. Limiting for mixes will be done on consumer decode side. Please continue to measure True Peak and mark as an FYI only. Branded Content QC External Verification.
Generally there will be a spec sheet for each broadcaster (i.e. ABC, CBS, BBC, etc) that your client will provide when asked. Spec sheets aren’t necessarily public or available online but some are (such as NBC Universal). Some online content providers (like Amazon), movie theater chains, and movie distributors also have specs, so it’s always good to ask.
Background on the average loudness spec
Before 2012, there used to only be one loudness spec: peak loudness. This was a brickwall limiter placed at the end of the chain. Back then, most television networks (in North America) had a peak level of -10dBfs. From the outside (especially coming from the music world) it seems like an odd way to mix – basically you’ve got 10 dB of empty headroom that you’re not allowed to use.
As long as your mix was limited at -10dB, it would pass QC even if it was squashed and sounded horrible. That’s what was happening, though, especially with commercials that were competing to be the loudest on the air. If you remember running for the remote every commercial break because they were uncomfortably louder, that was the issue.
Average Loudness Level & Audio Plugins That Measure It
In the US, Congress enacted the CALM act which went into effect in 2012 and required broadcasters to reign in these differences in loudness between programs and commercials. The spec that evolved from this was “average loudness level.” A loudness measurement covers the length of the entire piece, whether it’s a 30 second spot or a 2 hour movie. Average loudness is measured through a loudness meter. Popular measurement plugins are Izotope Insight, Waves WLM and Nugen VisLM. Dolby Media Meters was a standard for many years but is no longer being supported.
Important terms and concepts
To understand some important concepts, we’ll take a look at PBS’s most recent specs (2016), found here.
For PBS, it’s a 21-page document that includes requirements for video, audio, how to deliver, file naming, closed captioning, etc. It gets pretty detailed, but it’s a good example of what a spec sheet looks like and the types of audio requirements that come up. The information in the spec sheet will dictate some details in your session, such as track layouts for 5.1, where your limiters should be set, dialog level, bars and tones, etc. We’ll break down a few of these important elements.
PBS Technical Operating Specification 2016 – Part 1, Page 6 Sections 4.4.1, 4.4.2 – Audio Loudness Requirements
The three most important details to look for on a spec sheet are peak loudness, average loudness, and the ITU BS 1770 algorithm. These will be explained in detail below. In this case, the PBS specs are:
Peak Loudness: -2dBTP (“true peak” or 2 dB below full scale). This is your brickwall limiter on the master buss/output of the mix. In this case, it would be set to -2dB.
Average Loudness: – 24dB LKFS +/-2 LU. LKFS is the US standard (under ITU BS.1770) and LUFS is the European standard (EBU).
ITU BS 1770 Algorithm: ITU-R BS.1770-3. This is the algorithm used to measure average loudness.
The ITU developed an algorithm (ITU BS 1770) to calculate average loudness. The latest algorithm is 1770-4 (still used in 2018). In technical terms, loudness is an LEQ reading using a K-weighting and full-scale; the designation for this reading is “dB LKFS”. In the PBS spec sheet, section 4.4.1 and 4.4.2 say mixes should use ITU BS 1770-3, which is an older algorithm. This is an important detail, though, because when you’re measuring your mix, the plugin has to be set to the correct algorithm or the reading may be off. The PBS specs were written in 2016 (before 1770-4 came out). Broadcasters update these every couple of years, especially as technology changes.
In this PBS spec, the optimal average loudness is -24dB LKFS, but there is an acceptable loudness range (LRA) above and below +/-2 LU (“Loudness Units”). Basically that means your average loudness measurement can fall on or between -26dB LKFS and -22dB LKFS, but ideally you want to mix to hit at -24dB LKFS. The measurement plugin will probably show a short term and a long term value. The short term reading may jump all over the place (including beyond your in-spec numbers). The overall (long) reading is the important one. If the overall reading is out of range, it’s out of spec, won’t pass QC and will likely be rejected for air. Or, it may hit air with an additional broadcast limiter than squashes the mix (and doesn’t sound good).
As HD television has become more popular, broadcasters have loosened up on the peak loudness range. PBS is pretty liberal with -2dBTP (or -2dBfs); some broadcasters are at -6dBfs and occasionally some are still at -10dBfs.
The challenges of working with loudness specs
When the CALM Act went into effect, re-recording mixers thought loudness metering would be restrictive to creative mixing. Average loudness is measured across the entire program so there’s still room for some dynamic range short term. Loudness specs can be a problem for certain content, though. For example, if you’re mixing a show with a cheering audience, the cheering is still picked up as dialog by the loudness meter. You could have a spec of -24dB LKFS (+/-2), mix the show host at -24dB LKFS (in spec), but every time the audience cheers the short term measurement is -14dB LKFS. The overall loudness measurement might be -18dB LKFS – which is way out of spec! So sometimes you end up mixing dialog on the low side or bringing down an audience more than feels natural to fall in spec.
Another difficulty of mixing with a loudness spec is making adjustments when your overall measurement is out of spec. A dB of LU (the unit of measurement for average loudness) is not the same as 1dBFS (full scale). If you drop the mix 1dB by volume automation, it’s not necessarily a 1dB change in average loudness. If you’re mixing a 30 second promo and the loudness level is out of spec it’s easy to adjust and recheck. If you’re mixing a 90 minute film, it takes a bit more work and time to finesse the mix and get a new measurement.
There’s software that will make these adjustments for you – basically you can tell the software what the specs are and it’ll make small adjustments so the mix will fall in spec. While this is a good tool to have in the toolbox, I encourage mixers to first learn how to adjust their mix by hand and ear to understand how loudness measurements and metering works.
Loudness Over Time
When a mix gets QCed, it’s measured for loudness over the entire length unless the spec sheet says otherwise. For a 30 second commercial, the loudness reading will be one value for 30 seconds. A tv show might be the whole program (like 42 minutes) or it might be each act (from commercial break to commercial break). The spec sheet will give that info. A movie will have a single reading based on runtime, etc. So, it’s ok to have dynamic range over the content as long as the overall loudness level is within spec. There will be some dynamic range naturally especially if you have action scenes, music with vocals, and so on. If you weren’t looking at a meter and just mixing, you might mix as loud as -14 and as low as -30 (for short periods of time). The spec sheet dictates the range – like “-24LKFS +/- 2dBLKFS” or -27 +/- 1dB. Usually there’s a couple dB of range around the main number and they measure with decimal points (so -22.0 could be in spec but -21.9 would not).
Tips for working with loudness specs
I find in general if dialog is sitting between -10 and -20dBfs (instantaneous highs and lows) and not over-compressed, the average loudness reading should fall pretty close to -24dB LKFS. When I first started mixing to an average loudness spec, my mixes were often averaging hot (-20 to -22dB LKFS) when spec was -24. My ear had become accustomed to the sound of compressed dialog hitting a limiter on the master buss. What I’ve learned is that if you’re mixing with your dialog close to -24 dB LKFS (or -27 for film) you can bypass the master limiter and it should sound pretty seamless when you put it back in. If you’re noticing a big sound change with the limiter in, the overall reading will probably fall on the hot side.
I’ve tried mixing a few different ways with meters – leaving the meter up all the time, for a while til my ear gets dialed in, or just checking from time to time during a mix. When you have the window up all the time, you do risk making choices based on metrics and not on your ears. At the same time, if you’re just mixing a scene of simple dialog (people having a conversation, no yelling, normal level background noise) having the meter up can help train your ear what that pocket sounds like. Now, when I start a long-form mix (or if I’m working in a room I’m not familiar with), I usually dial in my dialog with a loudness meter visible. I’ll pick a scene or a character and set my channel strip (compressor, EQ, de-esser, noise reduction etc) so the dialog mix lands right on -24dB LKFS. I do this to “dial in” my ear to that loudness. It then acts as a reference, essentially.
One thing I like about mixing with a loudness spec is you don’t have to mix at 82 or 85 dB. While a room is optimally tuned for these levels, I personally don’t always listen this loud (especially if it’s just me/no client or I anticipate a long mixing day). Having a loudness meter helps when jumping between reference monitors or playing back through a television, too. I can set the TV to whatever level is comfortable and know that my mix is still in spec. When I’m mixing in an unfamiliar room, seeing the average loudness reading helps me acclimate, too.
When there’s no loudness spec
I mix most projects to some sort of spec, even if the client says there are no specs. For indie films, I usually mix at -27dB LKFS and a limiter set to -2dBFS or -6dBFS (depending on the content). If an indie film gets picked up for distribution, the distributor may provide specs. Sometimes film festivals have specs that differ from the distributor, too. If you’ve already mixed with general specs in mind, it may not need adjusting down the road, or at least you will have a much better idea how much you’ll need to adjust to be in spec.
Article originally featured on Soundgirls.org
Table of Contents
- 3 Options
- 4 Writers
1 Synopsis
ffprobe [options] [input_url]
2 Description
ffprobe gathers information from multimedia streams and prints it inhuman- and machine-readable fashion.
For example it can be used to check the format of the container usedby a multimedia stream and the format and type of each media streamcontained in it.
If a url is specified in input, ffprobe will try to open andprobe the url content. If the url cannot be opened or recognized asa multimedia file, a positive exit code is returned.
ffprobe may be employed both as a standalone application or incombination with a textual filter, which may perform moresophisticated processing, e.g. statistical processing or plotting.
Options are used to list some of the formats supported by ffprobe orfor specifying which information to display, and for setting howffprobe will show it.
ffprobe output is designed to be easily parsable by a textual filter,and consists of one or more sections of a form defined by the selectedwriter, which is specified by the print_format option.
Sections may contain other nested sections, and are identified by aname (which may be shared by other sections), and an uniquename. See the output of sections.
Metadata tags stored in the container or in the streams are recognizedand printed in the corresponding 'FORMAT', 'STREAM' or 'PROGRAM_STREAM'section.
3 Options
All the numerical options, if not specified otherwise, accept a stringrepresenting a number as input, which may be followed by one of the SIunit prefixes, for example: ’K’, ’M’, or ’G’.
If ’i’ is appended to the SI unit prefix, the complete prefix will beinterpreted as a unit prefix for binary multiples, which are based onpowers of 1024 instead of powers of 1000. Appending ’B’ to the SI unitprefix multiplies the value by 8. This allows using, for example:’KB’, ’MiB’, ’G’ and ’B’ as number suffixes.
Options which do not take arguments are boolean options, and set thecorresponding value to true. They can be set to false by prefixingthe option name with 'no'. For example using '-nofoo'will set the boolean option with name 'foo' to false.
3.1 Stream specifiers
Some options are applied per-stream, e.g. bitrate or codec. Stream specifiersare used to precisely specify which stream(s) a given option belongs to.
A stream specifier is a string generally appended to the option name andseparated from it by a colon. E.g.
-codec:a:1 ac3
contains thea:1
stream specifier, which matches the second audio stream. Therefore, itwould select the ac3 codec for the second audio stream.A stream specifier can match several streams, so that the option is applied to allof them. E.g. the stream specifier in
-b:a 128k
matches all audiostreams.An empty stream specifier matches all streams. For example,
-codec copy
or -codec: copy
would copy all the streams without reencoding.Possible forms of stream specifiers are:
Matches the stream with this index. E.g.
-threads:1 4
would set thethread count for the second stream to 4. If stream_index is used as anadditional stream specifier (see below), then it selects stream numberstream_index from the matching streams. Stream numbering is based on theorder of the streams as detected by libavformat except when a program ID isalso specified. In this case it is based on the ordering of the streams in theprogram.stream_type is one of following: ’v’ or ’V’ for video, ’a’ for audio, ’s’for subtitle, ’d’ for data, and ’t’ for attachments. ’v’ matches all videostreams, ’V’ only matches video streams which are not attached pictures, videothumbnails or cover arts. If additional_stream_specifier is used, thenit matches streams which both have this type and match theadditional_stream_specifier. Otherwise, it matches all streams of thespecified type.
Matches streams which are in the program with the id program_id. Ifadditional_stream_specifier is used, then it matches streams which bothare part of the program and match the additional_stream_specifier.
Match the stream by stream id (e.g. PID in MPEG-TS container).
Matches streams with the metadata tag key having the specified value. Ifvalue is not given, matches streams that contain the given tag with anyvalue.
Matches streams with usable configuration, the codec must be defined and theessential information such as video dimension or audio sample rate must be present.
Note that in
ffmpeg
, matching by metadata will only work properly forinput files.3.2 Generic options
These options are shared amongst the ff* tools.
Show license.
Show help. An optional parameter may be specified to print help about a specificitem. If no argument is specified, only basic (non advanced) tooloptions are shown.
Possible values of arg are:
Print advanced tool options in addition to the basic tool options.
Print complete list of options, including shared and private optionsfor encoders, decoders, demuxers, muxers, filters, etc.
Print detailed information about the decoder named decoder_name. Use the-decoders option to get a list of all decoders.
Print detailed information about the encoder named encoder_name. Use the-encoders option to get a list of all encoders.
Print detailed information about the demuxer named demuxer_name. Use the-formats option to get a list of all demuxers and muxers.
Print detailed information about the muxer named muxer_name. Use the-formats option to get a list of all muxers and demuxers.
Print detailed information about the filter named filter_name. Use the-filters option to get a list of all filters.
Print detailed information about the bitstream filter named bitstream_filter_name.Use the -bsfs option to get a list of all bitstream filters.
Print detailed information about the protocol named protocol_name.Use the -protocols option to get a list of all protocols.
Show version.
Show available formats (including devices).
Show available demuxers.
Show available muxers.
Show available devices.
Show all codecs known to libavcodec.
Note that the term ’codec’ is used throughout this documentation as a shortcutfor what is more correctly called a media bitstream format.
Show available decoders.
Show all available encoders.
Show available bitstream filters.
Show available protocols.
Show available libavfilter filters.
Show available pixel formats.
Show available sample formats.
Show channel names and standard channel layouts.
Show recognized color names.
Show autodetected sources of the input device.Some devices may provide system-dependent source names that cannot be autodetected.The returned list cannot be assumed to be always complete.
Show autodetected sinks of the output device.Some devices may provide system-dependent sink names that cannot be autodetected.The returned list cannot be assumed to be always complete.
Set logging level and flags used by the library.
The optional flags prefix can consist of the following values:
Indicates that repeated log output should not be compressed to the first lineand the 'Last message repeated n times' line will be omitted.
Indicates that log output should add a
[level]
prefix to each messageline. This can be used as an alternative to log coloring, e.g. when dumping thelog to file.Flags can also be used alone by adding a ’+’/’-’ prefix to set/reset a singleflag without affecting other flags or changing loglevel. Whensetting both flags and loglevel, a ’+’ separator is expectedbetween the last flags value and before loglevel.
loglevel is a string or a number containing one of the following values:
Show nothing at all; be silent.
Only show fatal errors which could lead the process to crash, such asan assertion failure. This is not currently used for anything.
Only show fatal errors. These are errors after which the process absolutelycannot continue.
Show all errors, including ones which can be recovered from.
Show all warnings and errors. Any message related to possiblyincorrect or unexpected events will be shown.
Show informative messages during processing. This is in addition towarnings and errors. This is the default value.
Same as
info
, except more verbose.Show everything, including debugging information.
For example to enable repeated log output, add the
level
prefix, and setloglevel to verbose
:Another example that enables repeated log output without affecting currentstate of
level
prefix flag or loglevel:By default the program logs to stderr. If coloring is supported by theterminal, colors are used to mark errors and warnings. Log coloringcan be disabled setting the environment variable
AV_LOG_FORCE_NOCOLOR
, or can be forced settingthe environment variable AV_LOG_FORCE_COLOR
.Dump full command line and log output to a file named
program-YYYYMMDD-HHMMSS.log
in the currentdirectory.This file can be useful for bug reports.It also implies -loglevel debug
.Setting the environment variable
FFREPORT
to any value has thesame effect. If the value is a ’:’-separated key=value sequence, theseoptions will affect the report; option values must be escaped if theycontain special characters or the options delimiter ’:’ (see the“Quoting and escaping” section in the ffmpeg-utils manual).The following options are recognized:
set the file name to use for the report;
%p
is expanded to the nameof the program, %t
is expanded to a timestamp, %%
is expandedto a plain %
set the log verbosity level using a numerical value (see
-loglevel
).For example, to output a report to a file named ffreport.logusing a log level of
32
(alias for log level info
):Errors in parsing the environment variable are not fatal, and will notappear in the report.
Suppress printing banner.
All FFmpeg tools will normally show a copyright notice, build optionsand library versions. This option can be used to suppress printingthis information.
Allows setting and clearing cpu flags. This option is intendedfor testing. Do not use it unless you know what you’re doing.
Possible flags for this option are:
- ‘x86’
- ‘mmx’
- ‘mmxext’
- ‘sse’
- ‘sse2’
- ‘sse2slow’
- ‘sse3’
- ‘sse3slow’
- ‘ssse3’
- ‘atom’
- ‘sse4.1’
- ‘sse4.2’
- ‘avx’
- ‘avx2’
- ‘xop’
- ‘fma3’
- ‘fma4’
- ‘3dnow’
- ‘3dnowext’
- ‘bmi1’
- ‘bmi2’
- ‘cmov’
- ‘ARM’
- ‘armv5te’
- ‘armv6’
- ‘armv6t2’
- ‘vfp’
- ‘vfpv3’
- ‘neon’
- ‘setend’
- ‘AArch64’
- ‘armv8’
- ‘vfp’
- ‘neon’
- ‘PowerPC’
- ‘altivec’
- ‘Specific Processors’
- ‘pentium2’
- ‘pentium3’
- ‘pentium4’
- ‘k6’
- ‘k62’
- ‘athlon’
- ‘athlonxp’
- ‘k8’
3.3 AVOptions
These options are provided directly by the libavformat, libavdevice andlibavcodec libraries. To see the list of available AVOptions, use the-help option. They are separated into two categories:
These options can be set for any container, codec or device. Generic optionsare listed under AVFormatContext options for containers/devices and underAVCodecContext options for codecs.
These options are specific to the given container, device or codec. Privateoptions are listed under their corresponding containers/devices/codecs.
For example to write an ID3v2.3 header instead of a default ID3v2.4 toan MP3 file, use the id3v2_version private option of the MP3muxer:
All codec AVOptions are per-stream, and thus a stream specifiershould be attached to them:
In the above example, a multichannel audio stream is mapped twice for output.The first instance is encoded with codec ac3 and bitrate 640k.The second instance is downmixed to 2 channels and encoded with codec aac. A bitrate of 128k is specified for it usingabsolute index of the output stream.
Note: the -nooption syntax cannot be used for booleanAVOptions, use -option 0/-option 1.
Note: the old undocumented way of specifying per-stream AVOptions byprepending v/a/s to the options name is now obsolete and will beremoved soon.
3.4 Main options
Force format to use.
Show the unit of the displayed values.
Use SI prefixes for the displayed values.Unless the '-byte_binary_prefix' option is used all the prefixesare decimal.
Force the use of binary prefixes for byte values.
Use sexagesimal format HH:MM:SS.MICROSECONDS for time values.
Prettify the format of the displayed values, it corresponds to theoptions '-unit -prefix -byte_binary_prefix -sexagesimal'.
Set the output printing format.
writer_name specifies the name of the writer, andwriter_options specifies the options to be passed to the writer.
For example for printing the output in JSON format, specify:
For more details on the available output printing formats, see theWriters section below.
Print sections structure and section information, and exit. The outputis not meant to be parsed by a machine.
Select only the streams specified by stream_specifier. Thisoption affects only the options related to streams(e.g.
show_streams
, show_packets
, etc.).For example to show only audio streams, you can use the command:
To show only video packets belonging to the video stream with index 1:
Show payload data, as a hexadecimal and ASCII dump. Coupled with-show_packets, it will dump the packets’ data. Coupled with-show_streams, it will dump the codec extradata.
The dump is printed as the 'data' field. It may contain newlines.
Show a hash of payload data, for packets with -show_packets and forcodec extradata with -show_streams.
Show information about the error found when trying to probe the input.
The error information is printed within a section with name 'ERROR'.
Show information about the container format of the input multimediastream.
All the container format information is printed within a section withname 'FORMAT'.
Like -show_format, but only prints the specified entry of thecontainer format information, rather than all. This option may be given morethan once, then all specified entries will be shown.
This option is deprecated, use
show_entries
instead.Set list of entries to show.
Entries are specified according to the followingsyntax. section_entries contains a list of section entriesseparated by
:
. Each section entry is composed by a sectionname (or unique name), optionally followed by a list of entries localto that section, separated by ,
.If section name is specified but is followed by no
=
, allentries are printed to output, together with all the containedsections. Otherwise only the entries specified in the local sectionentries list are printed. In particular, if =
is specified butthe list of local entries is empty, then no entries will be shown forthat section.Note that the order of specification of the local section entries isnot honored in the output, and the usual display order will beretained.
The formal syntax is given by:
For example, to show only the index and type of each stream, and the PTStime, duration time, and stream index of the packets, you can specifythe argument:
To show all the entries in the section 'format', but only the codectype in the section 'stream', specify the argument:
To show all the tags in the stream and format sections:
To show only the
title
tag (if available) in the streamsections:Show information about each packet contained in the input multimediastream.
The information for each single packet is printed within a dedicatedsection with name 'PACKET'.
Show information about each frame and subtitle contained in the inputmultimedia stream.
The information for each single frame is printed within a dedicatedsection with name 'FRAME' or 'SUBTITLE'.
Show logging information from the decoder about each frame according tothe value set in loglevel, (see
-loglevel
). This option requires -show_frames
.The information for each log message is printed within a dedicatedsection with name 'LOG'.
Show information about each media stream contained in the inputmultimedia stream.
Each media stream information is printed within a dedicated sectionwith name 'STREAM'.
Show information about programs and their streams contained in the inputmultimedia stream.
Each media stream information is printed within a dedicated sectionwith name 'PROGRAM_STREAM'.
Show information about chapters stored in the format.
Each chapter is printed within a dedicated section with name 'CHAPTER'.
Count the number of frames per stream and report it in thecorresponding stream section.
Count the number of packets per stream and report it in thecorresponding stream section.
Read only the specified intervals. read_intervals must be asequence of interval specifications separated by ','.
ffprobe
will seek to the interval starting point, and willcontinue reading from that.Each interval is specified by two optional parts, separated by '%'.
The first part specifies the interval start position. It isinterpreted as an absolute position, or as a relative offset from thecurrent position if it is preceded by the '+' character. If this firstpart is not specified, no seeking will be performed when reading thisinterval.
The second part specifies the interval end position. It is interpretedas an absolute position, or as a relative offset from the currentposition if it is preceded by the '+' character. If the offsetspecification starts with '#', it is interpreted as the number ofpackets to read (not including the flushing packets) from the intervalstart. If no second part is specified, the program will read until theend of the input.
Note that seeking is not accurate, thus the actual interval startpoint may be different from the specified position. Also, when aninterval duration is specified, the absolute end time will be computedby adding the duration to the interval start point found by seekingthe file, rather than to the specified start value.
The formal syntax is given by:
A few examples follow.
- Seek to time 10, read packets until 20 seconds after the found seekpoint, then seek to position
01:30
(1 minute and thirtyseconds) and read packets until position01:45
. - Read only 42 packets after seeking to position
01:23
: - Read only the first 20 seconds from the start:
- Read from the start until position
02:30
:
Show private data, that is data depending on the format of theparticular shown element.This option is enabled by default, but you may need to disable itfor specific uses, for example when creating XSD-compliant XML output.
Show information related to program version.
Version information is printed within a section with name'PROGRAM_VERSION'.
Show information related to library versions.
Version information for each library is printed within a section withname 'LIBRARY_VERSION'.
Show information related to program and library versions. This is theequivalent of setting both -show_program_version and-show_library_versions options.
Show information about all pixel formats supported by FFmpeg.
Pixel format information for each format is printed within a sectionwith name 'PIXEL_FORMAT'.
Force bitexact output, useful to produce output which is not dependenton the specific build.
Read input_url.
4 Writers
A writer defines the output format adopted by
ffprobe
, and will beused for printing all the parts of the output.A writer may accept one or more arguments, which specify the optionsto adopt. The options are specified as a list of key=valuepairs, separated by ':'.
All writers support the following options:
Set string validation mode.
The following values are accepted.
24lfca
The writer will fail immediately in case an invalid string (UTF-8)sequence or code point is found in the input. This is especiallyuseful to validate input metadata.
Any validation error will be ignored. This will result in possiblybroken output, especially with the json or xml writer.
The writer will substitute invalid UTF-8 sequences or code points withthe string specified with the string_validation_replacement.
Default value is ‘replace’.
Set replacement string to use in case string_validation isset to ‘replace’.
In case the option is not specified, the writer will assume the emptystring, that is it will remove the invalid sequences from the inputstrings.
A description of the currently available writers follows.
4.1 default
Default format.
Print each section in the form:
Metadata tags are printed as a line in the corresponding FORMAT, STREAM orPROGRAM_STREAM section, and are prefixed by the string 'TAG:'.
A description of the accepted options follows.
If set to 1 specify not to print the key of each field. Default valueis 0.
If set to 1 specify not to print the section header and footer.Default value is 0.
4.2 compact, csv
Compact and CSV format.
The
csv
writer is equivalent to compact
, but supportsdifferent defaults.Each section is printed on a single line.If no option is specified, the output has the form:
Metadata tags are printed in the corresponding 'format' or 'stream'section. A metadata tag key, if printed, is prefixed by the string'tag:'.
The description of the accepted options follows.
Specify the character to use for separating fields in the output line.It must be a single printable character, it is '|' by default (',' forthe
csv
writer).If set to 1 specify not to print the key of each field. Its defaultvalue is 0 (1 for the
csv
writer).Set the escape mode to use, default to 'c' ('csv' for the
csv
writer).It can assume one of the following values:
Perform C-like escaping. Strings containing a newline (‘n’), carriagereturn (‘r’), a tab (‘t’), a form feed (‘f’), the escapingcharacter (‘’) or the item separator character SEP are escapedusing C-like fashioned escaping, so that a newline is converted to thesequence ‘n’, a carriage return to ‘r’, ‘’ to ‘’ andthe separator SEP is converted to ‘SEP’.
Perform CSV-like escaping, as described in RFC4180. Stringscontaining a newline (‘n’), a carriage return (‘r’), a double quote(‘'’), or SEP are enclosed in double-quotes.
Perform no escaping.
Print the section name at the beginning of each line if the value is
1
, disable it with value set to 0
. Default value is1
.4.3 flat
Flat format.
A free-form output where each line contains an explicit key=value, such as'streams.stream.3.tags.foo=bar'. The output is shell escaped, so it can bedirectly embedded in sh scripts as long as the separator character is analphanumeric character or an underscore (see sep_char option).
The description of the accepted options follows.
Separator character used to separate the chapter, the section name, IDs andpotential tags in the printed field key.
Default value is ‘.’.
Specify if the section name specification should be hierarchical. Ifset to 1, and if there is more than one section in the currentchapter, the section name will be prefixed by the name of thechapter. A value of 0 will disable this behavior.
Default value is 1.
4.4 ini
INI format output.
Print output in an INI based format.
The following conventions are adopted:
- all key and values are UTF-8
- ‘.’ is the subgroup separator
- newline, ‘t’, ‘f’, ‘b’ and the following characters areescaped
- ‘’ is the escape character
- ‘#’ is the comment indicator
- ‘=’ is the key/value separator
- ‘:’ is not used but usually parsed as key/value separator
This writer accepts options as a list of key=value pairs,separated by ‘:’.
The description of the accepted options follows.
Specify if the section name specification should be hierarchical. Ifset to 1, and if there is more than one section in the currentchapter, the section name will be prefixed by the name of thechapter. A value of 0 will disable this behavior.
Default value is 1.
4.5 json
JSON based format.
Each section is printed using JSON notation.
The description of the accepted options follows.
If set to 1 enable compact output, that is each section will beprinted on a single line. Default value is 0.
For more information about JSON, see http://www.json.org/.
4.6 xml
XML based format.
The XML output is described in the XML schema description fileffprobe.xsd installed in the FFmpeg datadir.
ラウドネス 24lkfs
An updated version of the schema can be retrieved at the urlhttp://www.ffmpeg.org/schema/ffprobe.xsd, which redirects to thelatest schema committed into the FFmpeg development source code tree.
Note that the output issued will be compliant to theffprobe.xsd schema only when no special global output options(unit, prefix, byte_binary_prefix,sexagesimal etc.) are specified.
The description of the accepted options follows.
If set to 1 specify if the output should be fully qualified. Defaultvalue is 0.This is required for generating an XML file which can be validatedthrough an XSD file.
If set to 1 perform more checks for ensuring that the output is XSDcompliant. Default value is 0.This option automatically sets fully_qualified to 1.
For more information about the XML format, seehttps://www.w3.org/XML/.
5 Timecode
ffprobe
supports Timecode extraction:- MPEG1/2 timecode is extracted from the GOP, and is available in the videostream details (-show_streams, see timecode).
- MOV timecode is extracted from tmcd track, so is available in the tmcdstream metadata (-show_streams, see TAG:timecode).
- DV, GXF and AVI timecodes are available in format metadata(-show_format, see TAG:timecode).
6 See Also
ffprobe-all,ffmpeg, ffplay,ffmpeg-utils,ffmpeg-scaler,ffmpeg-resampler,ffmpeg-codecs,ffmpeg-bitstream-filters,ffmpeg-formats,ffmpeg-devices,ffmpeg-protocols,ffmpeg-filters
7 Authors
The FFmpeg developers.
For details about the authorship, see the Git history of the project(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
git log
in the FFmpeg source directory, or browsing theonline repository at http://source.ffmpeg.org.Maintainers for the specific components are listed in the fileMAINTAINERS in the source code tree.
This document was generated on December 5, 2020 using makeinfo.
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