Hi All! I faced difficulties while trying to measure sound level for a multimedia file with multiple audio streams. Here is the background:
1) ffmpeg 4.2.2 and it was used in different OS (Windows, FreeBSD). 2) The source file: Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test1.mov': Metadata: major_brand : qt minor_version : 537199360 compatible_brands: qt creation_time : 2020-05-05T09:48:02.000000Z Duration: 01:01:15.04, start: 0.000000, bitrate: 29791 kb/s Stream #0:0(eng): Video: mpeg2video (Main) (xdvc / 0x63766478), yuv420p(tv, bt709, top coded first (swapped)), 1920x1080 [SAR 1:1 DAR 16:9], 26715 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc (default) Metadata: creation_time : 2020-05-05T09:48:02.000000Z handler_name : Apple Video Media Handler encoder : XDCAM EX 1080i50 (35 Mb/s VBR) timecode : 00:00:00:00 Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default) Metadata: creation_time : 2020-05-05T09:48:02.000000Z handler_name : Apple Sound Media Handler timecode : 00:00:00:00 Stream #0:2(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default) Metadata: creation_time : 2020-05-05T09:48:02.000000Z handler_name : Apple Sound Media Handler timecode : 00:00:00:00 Stream #0:3(eng): Data: none (tmcd / 0x64636D74) (default) Metadata: creation_time : 2020-05-05T11:14:47.000000Z handler_name : Time Code Media Handler timecode : 00:00:00:00 Unsupported codec with id 0 for input stream 3 And the stream #0:2 is empty (no sound at all)! This is important. 3) The way I used to measure the sound level: https://stackoverflow.com/questions/38056970/ffmpeg-txt-from-audio-levels The documentation (https://ffmpeg.org/ffmpeg-filters.html#astats-1) says that it's possible to set the channel number (starting from 1) or string 'Overall' for the integral value. I decided to print levels for 1st and 2nd audio streams separately and overall levels finally. Here is the command: ffprobe -hide_banner -f lavfi -i amovie=test1.mov,astats=metadata=1:reset=1 -show_entries frame=pkt_pts_time:frame_tags=lavfi.astats.1.Peak_level,lavfi.astats.2.Peak_level,lavfi.astats.Overall.Peak_level -of csv=p=0 And here is what I see: [mov,mp4,m4a,3gp,3g2,mj2 @ 0x80557b600] st: 0 edit list: 1 Missing key frame while searching for timestamp: 0 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x80557b600] st: 0 edit list 1 Cannot find an index entry before timestamp: 0. Input #0, lavfi, from 'amovie=/mnt/playout6/Playout/Trinity/Exxxotica/Media/test1.mov,astats=metadata=1:reset=1': Duration: N/A, start: 0.000000, bitrate: 1536 kb/s Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s 0.000000,-inf,-inf,-inf 0.021333,-inf,-inf,-inf 0.042667,-inf,-inf,-inf 0.064000,-inf,-inf,-inf 0.085333,-inf,-inf,-inf 0.106667,-inf,-inf,-inf 0.128000,-inf,-inf,-inf 0.149333,-inf,-inf,-inf 0.170667,-inf,-inf,-inf 0.192000,-inf,-inf,-inf 0.213333,-inf,-inf,-inf 0.234667,-inf,-inf,-inf 0.256000,-inf,-inf,-inf 0.277333,-inf,-inf,-inf 0.298667,-inf,-inf,-inf 0.320000,-inf,-inf,-inf 0.341333,-40.124683,-48.232659,-40.124683 0.362667,-24.450328,-20.442361,-20.442361 0.384000,-15.920450,-15.235541,-15.235541 0.405333,-17.108509,-13.644516,-13.644516 0.426667,-15.176011,-13.778167,-13.778167 0.448000,-14.284777,-14.921187,-14.284777 0.469333,-14.353691,-13.147619,-13.147619 0.490667,-15.612737,-13.749723,-13.749723 0.512000,-15.577617,-14.215043,-14.215043 0.533333,-15.476248,-14.472115,-14.472115 0.554667,-15.115377,-11.835565,-11.835565 0.576000,-15.372937,-13.422919,-13.422919 0.597333,-5.541789,-4.610649,-4.610649 0.618667,-13.954783,-10.754262,-10.754262 0.640000,-12.198213,-13.178989,-12.198213 0.661333,-13.894198,-14.257364,-13.894198 0.682667,-14.118886,-12.640048,-12.640048 0.704000,-13.659833,-14.141813,-13.659833 0.725333,-17.131342,-16.504812,-16.504812 0.746667,-18.004467,-18.494126,-18.004467 0.768000,-14.940412,-16.608238,-14.940412 0.789333,-13.574658,-13.259134,-13.259134 0.810667,-12.985351,-13.042276,-12.985351 0.832000,-9.460374,-9.366353,-9.366353 0.853333,-13.081630,-10.817579,-10.817579 0.874667,-14.097363,-15.270840,-14.097363 0.896000,-15.432269,-13.685421,-13.685421 0.917333,-16.315447,-14.210959,-14.210959 0.938667,-14.378635,-13.564543,-13.564543 ... It is a lie. The second audio stream is totally silent from the beginning to the end. Also, note that ffprobe mentioned the only audio stream and it was #0:0. Why? I decided to test audio streams separately and copied them to separate files, then checked the sound level. For the first stream: ffmpeg -hide_banner -i test1.mov -ss 00:01:00 -t 00:01:00 -map 0:a:0 test1.mp3 ffprobe -hide_banner -f lavfi -i amovie=test1.mp3,astats=metadata=1:reset=1 -show_entries frame=pkt_pts_time:frame_tags=lavfi.astats.1.RMS_level -of csv=p=0 The result is expectable: [mp3float @ 0000000 Input #0, lavfi, fr Duration: N/A, st Stream #0:0: Au 0.000000,-50.248303 0.024000,-53.384511 0.048000,-53.646786 0.072000,-48.221139 0.096000,-51.244874 0.120000,-53.856832 0.144000,-54.184842 0.168000,-52.673918 0.192000,-53.253474 0.216000,-49.317896 0.240000,-44.537543 0.264000,-43.784163 0.288000,-47.155750 0.312000,-37.411110 0.336000,-45.422727 0.360000,-39.557636 0.384000,-35.931526 0.408000,-27.129281 0.432000,-27.934319 0.456000,-30.063120 0.480000,-34.268751 0.504000,-32.415779 0.528000,-28.112756 ... For the second stream: ffmpeg -hide_banner -i test1.mov -ss 00:01:00 -t 00:01:00 -map 0:a:0 test2.mp3 ffprobe -hide_banner -f lavfi -i amovie=test2.mp3,astats=metadata=1:reset=1 -show_entries frame=pkt_pts_time:frame_tags=lavfi.astats.1.RMS_level -of csv=p=0 0.000000,-inf 0.024000,-inf 0.048000,-inf 0.072000,-inf 0.096000,-inf 0.120000,-inf 0.144000,-inf 0.168000,-inf 0.192000,-inf 0.216000,-inf 0.240000,-inf 0.264000,-inf 0.288000,-inf 0.312000,-inf 0.336000,-inf 0.360000,-inf 0.384000,-inf 0.408000,-inf 0.432000,-inf 0.456000,-inf 0.480000,-inf 0.504000,-inf 0.528000,-inf ... Yes, this is really empty. But when I had copied both audio streams into WMA and tested then, I saw a lie again. It seems ffprobe cannot measure the 2nd audio stream and this is a bug. Am I right? WBR Alex _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
