id summary reporter owner description type status priority component version resolution keywords cc blockedby blocking reproduced analyzed 566 Encoding AAC stereo audio which starts silently to mpeg-ts causes 0-channel audio output. tungj "When encoding a video with stereo audio which starts with 6 seconds of silence to mpeg-ts, 'ffprobe' on the output .ts reports it to have an audio track with 0 channels of audio despite the audio playing in FFplay and vlc. This means the 0-channel audio stream is lost (in newest GIT N-33724-gefb1ce2 FFmpeg with libfaac 1.28), or causes an 'encoding 0 channels is not allowed' error in older FFmpeg git-N-29122-gb8a4444 libfaac 1.26 builds when doing any encoding on that output later on. Encoding the video to mpeg-ts: {{{ tungj@tungj-ffmpeg:~/bugreport$ ffmpeg -y -i 'initialSilence.mp4' -f mpegts -t 10 -acodec libfaac -ab 40k -ar 22050 initialSilence.ts ffmpeg version N-33724-gefb1ce2, Copyright (c) 2000-2011 the FFmpeg developers built on Oct 17 2011 11:00:29 with gcc 4.4.3 configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-x11grab libavutil 51. 21. 0 / 51. 21. 0 libavcodec 53. 20. 1 / 53. 20. 1 libavformat 53. 16. 0 / 53. 16. 0 libavdevice 53. 4. 0 / 53. 4. 0 libavfilter 2. 43. 6 / 2. 43. 6 libswscale 2. 1. 0 / 2. 1. 0 libpostproc 51. 2. 0 / 51. 2. 0 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'initialSilence.mp4': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2avc1mp41 creation_time : 1970-01-01 00:00:00 encoder : Lavf53.16.0 Duration: 00:00:10.02, start: 0.000000, bitrate: 84 kb/s Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 200x200, 5 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc Metadata: creation_time : 1970-01-01 00:00:00 Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 72 kb/s Metadata: creation_time : 1970-01-01 00:00:00 [buffer @ 0xa9fc620] w:200 h:200 pixfmt:yuv420p tb:1/1000000 sar:0/1 sws_param: [mpegts @ 0xa9fc6e0] muxrate VBR, pcr every 2 pkts, sdt every 200, pat/pmt every 40 pkts Output #0, mpegts, to 'initialSilence.ts': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2avc1mp41 creation_time : 1970-01-01 00:00:00 encoder : Lavf53.16.0 Stream #0:0(und): Video: mpeg2video, yuv420p, 200x200, q=2-31, 200 kb/s, 90k tbn, 25 tbc Metadata: creation_time : 1970-01-01 00:00:00 Stream #0:1(und): Audio: aac, 22050 Hz, stereo, s16, 40 kb/s Metadata: creation_time : 1970-01-01 00:00:00 Stream mapping: Stream #0.0 -> #0.0 (h264 -> mpeg2video) Stream #0.1 -> #0.1 (aac -> libfaac) Press [q] to stop, [?] for help frame= 250 fps= 0 q=2.0 Lsize= 197kB time=00:00:09.96 bitrate= 161.7kbits/s video:124kB audio:34kB global headers:0kB muxing overhead 24.226776% }}} The mpegts stream claims to have zero channels: {{{ tungj@tungj-ffmpeg:~/bugreport$ ffmpeg -v 9 -loglevel 99 -i initialSilence.ts ffmpeg version N-33724-gefb1ce2, Copyright (c) 2000-2011 the FFmpeg developers built on Oct 17 2011 11:00:29 with gcc 4.4.3 configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-x11grab libavutil 51. 21. 0 / 51. 21. 0 libavcodec 53. 20. 1 / 53. 20. 1 libavformat 53. 16. 0 / 53. 16. 0 libavdevice 53. 4. 0 / 53. 4. 0 libavfilter 2. 43. 6 / 2. 43. 6 libswscale 2. 1. 0 / 2. 1. 0 libpostproc 51. 2. 0 / 51. 2. 0 [mpegts @ 0x9c24aa0] Format mpegts probed with size=2048 and score=100 [mpegts @ 0x9c24aa0] stream=0 stream_type=2 pid=100 prog_reg_desc= [mpegts @ 0x9c24aa0] stream=1 stream_type=f pid=101 prog_reg_desc= [aac @ 0x9c290c0] Unsupported bit depth: 0 [mpeg2video @ 0x9c288e0] Unsupported bit depth: 0 [mpegts @ 0x9c24aa0] max_analyze_duration 5000000 reached at 5000000 [NULL @ 0x9c290c0] start time is not set in estimate_timings_from_pts Input #0, mpegts, from 'initialSilence.ts': Duration: 00:00:09.96, start: 1.400000, bitrate: 161 kb/s Program 1 Metadata: service_name : Service01 service_provider: FFmpeg Stream #0:0[0x100], 127, 1/90000: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p, 200x200 [SAR 1:1 DAR 1:1], 1/50, 104857 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc Stream #0:1[0x101](und), 0, 1/90000: Audio: aac ([15][0][0][0] / 0x000F), 0 channels, s16 At least one output file must be specified }}} When doing futher processing, the original audio is lost in output.mp4: {{{ tungj@tungj-ffmpeg:~/bugreport$ ffmpeg -y -i 'initialSilence.ts' -vcodec copy -acodec libfaac -ab 40k -ar 22050 output.mp4 ffmpeg version N-33724-gefb1ce2, Copyright (c) 2000-2011 the FFmpeg developers built on Oct 17 2011 11:00:29 with gcc 4.4.3 configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-x11grab libavutil 51. 21. 0 / 51. 21. 0 libavcodec 53. 20. 1 / 53. 20. 1 libavformat 53. 16. 0 / 53. 16. 0 libavdevice 53. 4. 0 / 53. 4. 0 libavfilter 2. 43. 6 / 2. 43. 6 libswscale 2. 1. 0 / 2. 1. 0 libpostproc 51. 2. 0 / 51. 2. 0 [mpegts @ 0x9346aa0] max_analyze_duration 5000000 reached at 5000000 [NULL @ 0x934b0c0] start time is not set in estimate_timings_from_pts Input #0, mpegts, from 'initialSilence.ts': Duration: 00:00:09.96, start: 1.400000, bitrate: 161 kb/s Program 1 Metadata: service_name : Service01 service_provider: FFmpeg Stream #0:0[0x100]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p, 200x200 [SAR 1:1 DAR 1:1], 104857 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc Stream #0:1[0x101](und): Audio: aac ([15][0][0][0] / 0x000F), 0 channels, s16 Output #0, mp4, to 'output.mp4': Metadata: encoder : Lavf53.16.0 Stream #0:0: Video: mpeg2video (a[0][0][0] / 0x0061), yuv420p, 200x200 [SAR 1:1 DAR 1:1], q=2-31, 104857 kb/s, 25 tbn, 25 tbc Stream mapping: Stream #0.0 -> #0.0 (copy) Press [q] to stop, [?] for help frame= 250 fps= 0 q=-1.0 Lsize= 127kB time=00:00:09.96 bitrate= 104.5kbits/s video:124kB audio:0kB global headers:0kB muxing overhead 2.308019% }}} Details of the input file: {{{ tungj@tungj-ffmpeg:~/bugreport$ ffmpeg -v 9 -loglevel 99 -i initialSilence.mp4 ffmpeg version N-33724-gefb1ce2, Copyright (c) 2000-2011 the FFmpeg developers built on Oct 17 2011 11:00:29 with gcc 4.4.3 configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-x11grab libavutil 51. 21. 0 / 51. 21. 0 libavcodec 53. 20. 1 / 53. 20. 1 libavformat 53. 16. 0 / 53. 16. 0 libavdevice 53. 4. 0 / 53. 4. 0 libavfilter 2. 43. 6 / 2. 43. 6 libswscale 2. 1. 0 / 2. 1. 0 libpostproc 51. 2. 0 / 51. 2. 0 [mov,mp4,m4a,3gp,3g2,mj2 @ 0xa374aa0] Format mov,mp4,m4a,3gp,3g2,mj2 probed with size=2048 and score=100 [mov,mp4,m4a,3gp,3g2,mj2 @ 0xa374aa0] ISO: File Type Major Brand: isom [aac @ 0xa3852a0] Unsupported bit depth: 0 [h264 @ 0xa37b5c0] no picture Last message repeated 1 times [mov,mp4,m4a,3gp,3g2,mj2 @ 0xa374aa0] All info found Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'initialSilence.mp4': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2avc1mp41 creation_time : 1970-01-01 00:00:00 encoder : Lavf53.16.0 Duration: 00:00:10.02, start: 0.000000, bitrate: 84 kb/s Stream #0:0(und), 3, 1/25: Video: h264 (High) (avc1 / 0x31637661), yuv420p, 200x200, 1/50, 5 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc Metadata: creation_time : 1970-01-01 00:00:00 Stream #0:1(und), 1, 1/48000: Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 72 kb/s Metadata: creation_time : 1970-01-01 00:00:00 At least one output file must be specified }}} Interestingly, the problem seems to occur at the silence-to-audio boundary; encoding either before the sound starts ffmpeg -y -i 'initialSilence.mp4' -f mpegts -t 5 -acodec libfaac -ab 40k -ar 22050 initialSilence.ts or after the silence ends ffmpeg -y -i 'initialSilence.mp4' -f mpegts -ss 8 -acodec libfaac -ab 40k -ar 22050 initialSilence.ts produce mpegts files which ffprobe reports as having stereo audio output." defect closed normal avformat git-master fixed aac mpegts 1 0