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La conservation du net art au musée. Les stratégies à l’œuvre
26 mai 2011
Mis à jour : Juillet 2013
Langue : français
Type : Texte
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13 avril 2011Unfortunately a software is never perfect.
If you think you have found a bug, report it using our ticket system. Please to help us to fix it by providing the following information : the browser you are using, including the exact version as precise an explanation as possible of the problem if possible, the steps taken resulting in the problem a link to the site / page in question
If you think you have solved the bug, fill in a ticket and attach to it a corrective patch.
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Supporting all media types
13 avril 2011, parUnlike most software and media-sharing platforms, MediaSPIP aims to manage as many different media types as possible. The following are just a few examples from an ever-expanding list of supported formats : images : png, gif, jpg, bmp and more audio : MP3, Ogg, Wav and more video : AVI, MP4, OGV, mpg, mov, wmv and more text, code and other data : OpenOffice, Microsoft Office (Word, PowerPoint, Excel), web (html, CSS), LaTeX, Google Earth and (...)
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HTML5 audio and video support
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Sur d’autres sites (8006)
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How to extract audio in ffmpeg from mov file
3 août 2020, par David542I have a ProRes422 file with a
.movcontainer :FINAL.mov. I would like to save out the audio track to a new file (no encoding or anything, just save it out). In QuickTime there is an option to save "Audio Only" —



What would be the equivalent way to do this within
ffmpeg? From basic research it seems something along the lines of :

$ ffmpeg \
 -i FINAL.mov \
 -vn # remove video? \
 ?? # keep audio \ 
 MYAUDIO_FINAL.mov


$ ffmpeg -igives :

Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'FINAL.mov':
 Metadata:
 major_brand : qt
 minor_version : 537199360
 compatible_brands: qt
 creation_time : 2016-01-11T19:23:10.000000Z
 com.apple.finalcutstudio.media.uuid: CE6F1278-8982-4B98-9E46-AE7C329436EF
 com.apple.quicktime.player.movie.audio.gain: 1.000000
 com.apple.quicktime.player.movie.audio.treble: 0.000000
 com.apple.quicktime.player.movie.audio.bass: 0.000000
 com.apple.quicktime.player.movie.audio.balance: 0.000000
 com.apple.quicktime.player.movie.audio.pitchshift: 0.000000
 com.apple.quicktime.player.movie.audio.mute:
 com.apple.quicktime.player.movie.visual.brightness: 0.000000
 com.apple.quicktime.player.movie.visual.color: 1.000000
 com.apple.quicktime.player.movie.visual.tint: 0.000000
 com.apple.quicktime.player.movie.visual.contrast: 1.000000
 com.apple.quicktime.player.version: 7.6.6 (7.6.6)
 com.apple.quicktime.version: 7.7.3 (2826.24) 0x7738000 (Mac OS X, 10.9.5, 13F34)
 Duration: 00:01:59.58, start: 0.000000, bitrate: 154872 kb/s
 Stream #0:0(eng): Video: prores (apch / 0x68637061), yuv422p10le(bt709, progressive), 1920x1080, 153307 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 23976 tbn, 23976 tbc (default)
 Metadata:
 creation_time : 2016-01-11T19:23:10.000000Z
 handler_name : Apple Alias Data Handler
 encoder : Apple ProRes 422 (HQ)
 Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default)
 Metadata:
 creation_time : 2016-01-11T19:23:10.000000Z
 handler_name : Apple Alias Data Handler


And a second file with 8 channel audio :


Duration: 01:10:12.00, start: 0.000000, bitrate: 173231 kb/s
 Stream #0:0(eng): Video: prores (apch / 0x68637061), yuv422p10le(bt709, progressive), 1920x1080, 164007 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 encoder : Apple ProRes 422 (HQ)
 Stream #0:1(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (FL), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:2(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (FR), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:3(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:4(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (LFE), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:5(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (BL), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:6(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (BR), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:7(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (DL), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
 Stream #0:8(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (DR), s32 (24 bit), 1152 kb/s (default)
 Metadata:
 handler_name : Apple Alias Data Handler
At least one output file must be specified


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FFmpeg downmuxing multiple tracks with custom "af"s
26 août 2020, par CasualDemonI am trying to do a custom downmix conversion, that is the rough equivalent of :


ffmpeg -y -i "file.mkv" \
 -map 0:1 -c:0 flac -ac:0 4 \
 -map 0:3 -c:1 flac -ac:1 3 \
 -map 0:3 -c:2 flac -ac:2 3 \
 audio.mkv


I tried using the command :


ffmpeg -y -i "file.mkv" \
 -map 0:1 -c:0 flac -af:0 "pan=3.1| FL < FL + 0.6*BL + 0.6*SL | FR < FR + 0.6*BR + 0.6*SR | FC = FC | LFE = LFE" \
 -map 0:3 -c:1 flac -af:1 "pan=2.1| FL < FL + 0.6*BL + 0.6*SL + 0.5*FC | FR < FR + 0.6*BR + 0.6*SR + 0.5*FC | LFE = LFE" \
 -map 0:3 -c:2 flac -af:2 "pan=2.1| FL < FL + 0.6*BL + 0.6*SL + 0.5*FC + 0.5*LFE | FR < FR + 0.6*BR + 0.6*SR + 0.5*FC + 0.5*LFE" \
 audio.mkv


But it gave an error that only 1 "af" is supported, unlike "ac" :


Only '-af pan=2.1| FL < FL + 0.6*BL + 0.6*SL + 0.5*FC + 0.5*LFE | FR < FR + 0.6*BR + 0.6*SR + 0.5*FC + 0.5*LFE | LFE = FC' read, ignoring remaining -af options: Use ',' to separate filters


So I tried doing as it said, and separated them with a comma :


ffmpeg -y -i "file.mkv" \
 -map 0:1 -c:0 flac \
 -map 0:3 -c:1 flac \
 -map 0:3 -c:2 flac \
 -af "pan=3.1| FL < FL + 0.6*BL + 0.6*SL | FR < FR + 0.6*BR + 0.6*SR | FC = FC | LFE = LFE,pan=2.1| FL < FL + 0.6*BL + 0.6*SL + 0.5*FC | FR < FR + 0.6*BR + 0.6*SR + 0.5*FC | LFE = LFE,pan=2.1| FL < FL + 0.6*BL + 0.6*SL + 0.5*FC + 0.5*LFE | FR < FR + 0.6*BR + 0.6*SR + 0.5*FC + 0.5*LFE | LFE = LFE" \
 audio.mkv


Which started the encoding, but I noticed that it was only applying the last pan, and all three tracks were being downmixed to the last 2.1 !


According to the documentation, https://ffmpeg.org/ffmpeg-filters.html#Filtergraph-syntax-1 adding a "," is creating a "filterchain" which I don't think I want, as I am doing the same filter on three different tracks. So I am at a loss of what I am supposed to do from there.


Thanks for any help !


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FFmpeg - generate x264 CBR video transport stream with C-API
6 juillet 2020, par ZeroDefectUsing various posts sprinkled around the Internet, including this one here on SO, I've been able to understand how to use the FFmpeg cli to generate a CBR video bitrate using the x264 codec (wrapped in an MPEG-2 transport stream). Note : I'm concerned with the video bitrate - nothing else.


ffmpeg -i cbr_test_file_input.mp4 -c:v libx264 -pix_fmt yuv420p -b:v 6000000 -preset fast -tune film -g 25 -x264-params vbv-maxrate=6000:vbv-bufsize=6000:force-cfr=1:nal-hrd=cbr -flags +ildct+ilme x264_cbr_test_output.ts


However, I'm trying to approach this from an FFmpeg C-API point of view. I'm having issues. I've knocked together some code to try do something very similar to what is being done in the FFmpeg CLI. I can generate a transport stream of what I think should be CBR, but the profile of the video bitrate is very different from what I thought was the FFmpeg cli equivalent :


The initialisation of the AVCodecContext looks something like :


av_dict_set(&pDict, "preset", "faster", 0);
 av_dict_set(&pDict, "tune", "film", 0);
 av_dict_set_int(&pDict, "rc-lookahead", 25, 0);

 pCdcCtxOut->width = pCdcCtxIn->width;
 pCdcCtxOut->height = pCdcCtxIn->height;
 pCdcCtxOut->pix_fmt = AV_PIX_FMT_YUV420P;
 pCdcCtxOut->gop_size = 25;

 // Going for 6Mbit/s
 pCdcCtxOut->bit_rate = 6000000;
 //pCdcCtxOut->rc_min_rate = pCdcCtxOut->bit_rate;
 pCdcCtxOut->rc_max_rate = pCdcCtxOut->bit_rate;
 pCdcCtxOut->rc_buffer_size = pCdcCtxOut->bit_rate;
 pCdcCtxOut->rc_initial_buffer_occupancy = static_cast<int>((pCdcCtxOut->bit_rate * 9) / 10);

 std::string strParams = "vbv-maxrate="
 + std::to_string(pCdcCtxOut->bit_rate / 1000)
 + ":vbv-bufsize="
 + std::to_string(pCdcCtxOut->bit_rate / 1000)
 + ":force-cfr=1:nal-hrd=cbr";

 av_dict_set(&pDict, "x264-params", strParams.c_str(), 0);

 pCdcCtxOut->field_order = AV_FIELD_TT;
 pCdcCtxOut->flags = (AV_CODEC_FLAG_INTERLACED_DCT | AV_CODEC_FLAG_INTERLACED_ME | AV_CODEC_FLAG_CLOSED_GOP);

 // WARN: Make some assumptions here!
 pCdcCtxOut->time_base = AVRational{1,25};
 pCdcCtxOut->framerate = AVRational{25,1};
 pCdcCtxOut->sample_aspect_ratio = AVRational{64,45};
</int>

The output graphs appear very different :




Above is the FFmpeg CLI output - video bitrate holds fairly steady.




Above is the output of my sample application - some significant dips in the video bitrate.


I've taken this a step further and created a git repo consisting of :


- 

- Code of sample application
- Test input file (.mp4)
- Outputs (.ts file) of tests
- Graphs of output bitrates.










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