Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
> > > > Ok, I've cheated somewhat, and taken my (much older) ffmpeg and > editted isom.c so that rather than substituting 0x40 for AV_CODEC_ID_AAC it > now substitutes 0x67 instead. If I look at the resulting output file with > mp4info and the output of FFmpeg itself they both show that it's MP4 AAC > LC. However, the codec string given by mp4info is mp4a.67. If I want to > send it to a web page it has to be AAC LC, but the typically accepted codec > string is mp4a.40.2 which is also supposed to map to AAC LC. So now I am > wondering how I would encode that in the ESDS or similar so that a) mp4info > is happy that it's mp4a.40.2 and that the chrome video decoder is happy > with the media type (because mp4a.67 codec string although in theory > supported gives me "Unrecognised media codec: mp4a.67" in Chrome. > > > Another update: I've updated movenc.c now, having reverted isom.c to original. This (as I'm only ever dealing with AAC_LC) hacks the decoder specific info len to force an extra 10 bytes if the track->par->codec_id = AV_CODEC_ID_AAC. And then later on where decoder specific info is inserted from vos_len and vos_data (I couldn't find where these get set - hence me doing it this way) I force these to insert the extra info required to make it think it's mp4a.40.2. This was done by comparing the esds packet from a faulty encoding and from the correct encoding. The correct encoding for mp4a.40.2 adds a descriptor of 5, length 5, and then the bytes: 0x11 0x90 0x56 0xe5 0x00 mp4info accepts this is mp4a.40.2 and so does Chrome. Thank you again for pointing me in the right direction, and apologies that I've hacked ffmpeg purely for my purposes without finding a "proper" solution. Cheers, Simon ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
> > > > So it seems to be a matter of TS demuxing passing along the codec > extradata correctly. > > Regards, > Tobias > > Thank you both for your replies. Ok, I've cheated somewhat, and taken my (much older) ffmpeg and editted isom.c so that rather than substituting 0x40 for AV_CODEC_ID_AAC it now substitutes 0x67 instead. If I look at the resulting output file with mp4info and the output of FFmpeg itself they both show that it's MP4 AAC LC. However, the codec string given by mp4info is mp4a.67. If I want to send it to a web page it has to be AAC LC, but the typically accepted codec string is mp4a.40.2 which is also supposed to map to AAC LC. So now I am wondering how I would encode that in the ESDS or similar so that a) mp4info is happy that it's mp4a.40.2 and that the chrome video decoder is happy with the media type (because mp4a.67 codec string although in theory supported gives me "Unrecognised media codec: mp4a.67" in Chrome. Regards, Simon ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
On 24.05.2021 22:26, Moritz Barsnick wrote: On Wed, May 19, 2021 at 12:17:38 +0200, Tobias Rapp wrote: Looks like the data that should be found in the "esds" atom is missing or incomplete when using -c:a copy. See this link for details on how AAC profile information is stored in MP4: https://stackoverflow.com/questions/3987850/mp4-atom-how-to-discriminate-the-audio-codec-is-it-aac-or-mp3 Interesting stuff. Don't know enough about TS (de)muxing, though, to find out where this profile data should be parsed out from the input by FFmpeg. MPEG-TS and demuxing isn't the problem. If you look at the ffmpeg output in the original e-mail from decoding the file, it correctly identifies the codec as "aac (LC)". The issue is the encoding to MP4. The reason is that the AAC variants have only one codec tag AV_CODEC_ID_AAC, and that needs to map to various tags, e.g. 0x40 for AAC and 0x67 for AAC LC. https://github.com/FFmpeg/FFmpeg/blob/3749eede66c3774799766b1f246afae8a6ffc9bb/libavformat/isom.c#L34 When writing the tag in the esds atom, there's no additional info available allowing mapping to 0x67, therefore 0x40 is written: https://github.com/FFmpeg/FFmpeg/blob/3749eede66c3774799766b1f246afae8a6ffc9bb/libavformat/movenc.c#L711 I have no idea how this info could be carried forward. From the StackOverflow answers the AAC profile seems to be part of the AudioSpecificConfig (ASC) part which is written as "TAG 5" within the Elementary Stream Descriptor MP4 atom. Looking at the FFmpeg movenc.c link you posted it is written some lines below the codec id from track->vos_data. This pointer is filled from AVCodecParameters->extradata in ff_mov_write_packet: https://github.com/FFmpeg/FFmpeg/blob/3749eede66c3774799766b1f246afae8a6ffc9bb/libavformat/movenc.c#L5586 So it seems to be a matter of TS demuxing passing along the codec extradata correctly. Regards, Tobias ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
On Mon, May 24, 2021 at 22:26:03 +0200, Moritz Barsnick wrote: > MPEG-TS and demuxing isn't the problem. If you look at the ffmpeg > output in the original e-mail from decoding the file, it correctly > identifies the codec as "aac (LC)". The issue is the encoding to MP4. On the other hand, when I copy AAC LC audio from MPEG-TS to MP4, it works. So my analysis has some major flaw. Moritz ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
On Wed, May 19, 2021 at 12:17:38 +0200, Tobias Rapp wrote: > Looks like the data that should be found in the "esds" atom is missing or > incomplete when using -c:a copy. See this link for details on how AAC > profile information is stored in MP4: > > https://stackoverflow.com/questions/3987850/mp4-atom-how-to-discriminate-the-audio-codec-is-it-aac-or-mp3 Interesting stuff. > Don't know enough about TS (de)muxing, though, to find out where this > profile data should be parsed out from the input by FFmpeg. MPEG-TS and demuxing isn't the problem. If you look at the ffmpeg output in the original e-mail from decoding the file, it correctly identifies the codec as "aac (LC)". The issue is the encoding to MP4. The reason is that the AAC variants have only one codec tag AV_CODEC_ID_AAC, and that needs to map to various tags, e.g. 0x40 for AAC and 0x67 for AAC LC. https://github.com/FFmpeg/FFmpeg/blob/3749eede66c3774799766b1f246afae8a6ffc9bb/libavformat/isom.c#L34 When writing the tag in the esds atom, there's no additional info available allowing mapping to 0x67, therefore 0x40 is written: https://github.com/FFmpeg/FFmpeg/blob/3749eede66c3774799766b1f246afae8a6ffc9bb/libavformat/movenc.c#L711 I have no idea how this info could be carried forward. Moritz ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
On 14.05.2021 15:31, Simon Brown wrote: [...] For although there it says aac (LC) if I run mp4info on the resultant file I get this: [...] Track 2: flags:3 ENABLED IN-MOVIE id: 2 type: Audio duration: 0 ms language: und media: sample count: 0 timescale:48000 duration: 0 (media timescale units) duration: 0 (ms) bitrate (computed): 125.373 Kbps sample count with fragments: 848 duration with fragments: 868354 duration with fragments: 18091 (ms) Sample Description 0 Coding: mp4a (MPEG-4 Audio) Stream Type: Audio Object Type: MPEG-4 Audio Max Bitrate: 128250 Avg Bitrate: 0 Buffer Size: 0 Codecs String: mp4a.40.0 MPEG-4 Audio Object Type: 0 (UNKNOWN) Sample Rate: 48000 Sample Size: 16 Channels:2 whereas if I used -c:a aac -profile:a aac_low instead of -c:a copy then I get this from mp4info: Track 2: flags:3 ENABLED IN-MOVIE id: 2 type: Audio duration: 0 ms language: und media: sample count: 0 timescale:48000 duration: 0 (media timescale units) duration: 0 (ms) bitrate (computed): 49.589 Kbps sample count with fragments: 849 duration with fragments: 869378 duration with fragments: 18112 (ms) Sample Description 0 Coding: mp4a (MPEG-4 Audio) Stream Type: Audio Object Type: MPEG-4 Audio Max Bitrate: 128000 Avg Bitrate: 0 Buffer Size: 0 Codecs String: mp4a.40.2 MPEG-4 Audio Object Type: 2 (AAC Low Complexity) MPEG-4 Audio Decoder Config: Sampling Frequency: 48000 Channels: 2 Extension: Object Type: Spectral Band Replication SBR Present: no PS Present: no Sampling Frequency: 0 Sample Rate: 48000 Sample Size: 16 Channels:2 where it clearly states it as Mpeg-4 Audio AAC Low complexity. Looks like the data that should be found in the "esds" atom is missing or incomplete when using -c:a copy. See this link for details on how AAC profile information is stored in MP4: https://stackoverflow.com/questions/3987850/mp4-atom-how-to-discriminate-the-audio-codec-is-it-aac-or-mp3 Don't know enough about TS (de)muxing, though, to find out where this profile data should be parsed out from the input by FFmpeg. Regards, Tobias ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
On Mon, May 17, 2021 at 23:34:45 +0100, Simon Brown wrote: > Thank you for your reply. If it is the bitstream filter could you point me > to the relevant source file that is responsible for this filter? Sure, it's here: https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/aac_adtstoasc_bsf.c > mp4info doesn't deal with TS, as you surmise. FFMpeg reports the output > file as AAC (not LC). I'm not sure VLC gives that detail. But given that > the ffmpeg processor and the mp4info program both seem to concur when there > is or isn't AAC-LC I'm not sure there is much value in trying a third > tool. You could also try mediainfo. I also found a tool capable of parsing and deconstruction AAC headers (https://p23.nl/projects/aac-header/), but I don't trust it since it isn't capable of recognizing e.g. HE-AACv2 (though I haven't taken the time to understand all the headers myself). I couldn't reproduce the loss of this information with the input samples I have. Can you share your input file? Since it's an MPEG-TS. perhaps the first MB (or five) suffice. > I will download the latest prebuilt binaries for Windows and give it a try > with those. I'd still be interested in the source file responsible as the > version on the embedded system I'm using is not the most recent build, and > rebuilding for that isn't something I want to do at this stage. I understand. Cheers, Moritz ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
> > > On Fri, May 14, 2021 at 14:31:42 +0100, Simon Brown wrote: > > Hi, > > I have a mpeg2 transport stream with video as H264 and audio as AAC LC. > If > > I use the following command to convert it to fragmented MP4 by just > copying > > the encoded data, then the result is now AAC, and not AAC LC. If > instead I > > re-encode with AAC asking for profile:a aac_low then I get AAC LC. But > if > > the input source is AAC LC why would it change the output type to AAC? > > > > ffmpeg.exe -f mpegts -fflags +nobuffer+nofillin -probesize 500 -i > > soc_udp_rx_02.ts -c:a copy -bsf:a aac_adtstoasc -c:v copy -f mp4 > > -frag_duration 8 -movflags +empty_moov+default_base_moof -metadata > > title="media source exentions" testaudio.mp4 > > This shouldn't change anything in the AAC stream, unless the bitstream > filter is capable of ruining it. > > What does it say about the original? (Nothing, presumably, because it's > MPEG-TS.) What does ffmpeg say about the output file? Do you have any > other tool which can use to check? > > Cheers, > Moritz > > Hi Moritz, Thank you for your reply. If it is the bitstream filter could you point me to the relevant source file that is responsible for this filter? mp4info doesn't deal with TS, as you surmise. FFMpeg reports the output file as AAC (not LC). I'm not sure VLC gives that detail. But given that the ffmpeg processor and the mp4info program both seem to concur when there is or isn't AAC-LC I'm not sure there is much value in trying a third tool. I will download the latest prebuilt binaries for Windows and give it a try with those. I'd still be interested in the source file responsible as the version on the embedded system I'm using is not the most recent build, and rebuilding for that isn't something I want to do at this stage. Regards, Simon ___ 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".
Re: [FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
On Fri, May 14, 2021 at 14:31:42 +0100, Simon Brown wrote: > Hi, > I have a mpeg2 transport stream with video as H264 and audio as AAC LC. If > I use the following command to convert it to fragmented MP4 by just copying > the encoded data, then the result is now AAC, and not AAC LC. If instead I > re-encode with AAC asking for profile:a aac_low then I get AAC LC. But if > the input source is AAC LC why would it change the output type to AAC? > > ffmpeg.exe -f mpegts -fflags +nobuffer+nofillin -probesize 500 -i > soc_udp_rx_02.ts -c:a copy -bsf:a aac_adtstoasc -c:v copy -f mp4 > -frag_duration 8 -movflags +empty_moov+default_base_moof -metadata > title="media source exentions" testaudio.mp4 This shouldn't change anything in the AAC stream, unless the bitstream filter is capable of ruining it. > ffmpeg version git-2020-06-19-2f59946 Copyright (c) 2000-2020 the FFmpeg > developers This is a bit old, please retry with a recent build. > For although there it says aac (LC) if I run mp4info on the resultant file > I get this: > > mp4info testaudio.mp4 [...] > Track 2: > flags:3 ENABLED IN-MOVIE > id: 2 > type: Audio > duration: 0 ms > language: und > media: > sample count: 0 > timescale:48000 > duration: 0 (media timescale units) > duration: 0 (ms) > bitrate (computed): 125.373 Kbps > sample count with fragments: 848 > duration with fragments: 868354 > duration with fragments: 18091 (ms) > Sample Description 0 > Coding: mp4a (MPEG-4 Audio) > Stream Type: Audio > Object Type: MPEG-4 Audio > Max Bitrate: 128250 > Avg Bitrate: 0 > Buffer Size: 0 > Codecs String: mp4a.40.0 > MPEG-4 Audio Object Type: 0 (UNKNOWN) > Sample Rate: 48000 > Sample Size: 16 > Channels:2 What does it say about the original? (Nothing, presumably, because it's MPEG-TS.) What does ffmpeg say about the output file? Do you have any other tool which can use to check? Cheers, Moritz ___ 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".
[FFmpeg-user] Preserving AAC LC status when converting to fragmented MP4
Hi, I have a mpeg2 transport stream with video as H264 and audio as AAC LC. If I use the following command to convert it to fragmented MP4 by just copying the encoded data, then the result is now AAC, and not AAC LC. If instead I re-encode with AAC asking for profile:a aac_low then I get AAC LC. But if the input source is AAC LC why would it change the output type to AAC? ffmpeg.exe -f mpegts -fflags +nobuffer+nofillin -probesize 500 -i soc_udp_rx_02.ts -c:a copy -bsf:a aac_adtstoasc -c:v copy -f mp4 -frag_duration 8 -movflags +empty_moov+default_base_moof -metadata title="media source exentions" testaudio.mp4 ffmpeg version git-2020-06-19-2f59946 Copyright (c) 2000-2020 the FFmpeg developers built with gcc 9.3.1 (GCC) 20200523 configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf libavutil 56. 55.100 / 56. 55.100 libavcodec 58. 93.100 / 58. 93.100 libavformat58. 47.100 / 58. 47.100 libavdevice58. 11.100 / 58. 11.100 libavfilter 7. 86.100 / 7. 86.100 libswscale 5. 8.100 / 5. 8.100 libswresample 3. 8.100 / 3. 8.100 libpostproc55. 8.100 / 55. 8.100 [h264 @ 01967ec1ec00] non-existing PPS 0 referenced Last message repeated 1 times [h264 @ 01967ec1ec00] decode_slice_header error [h264 @ 01967ec1ec00] no frame! [h264 @ 01967ec1ec00] non-existing PPS 0 referenced Last message repeated 1 times [h264 @ 01967ec1ec00] decode_slice_header error [h264 @ 01967ec1ec00] no frame! [mpegts @ 01967ebfed00] start time for stream 0 is not set in estimate_timings_from_pts [mpegts @ 01967ebfed00] start time for stream 1 is not set in estimate_timings_from_pts [mpegts @ 01967ebfed00] Packet corrupt (stream = 0, dts = 590952620). [mpegts @ 01967ebfed00] Packet corrupt (stream = 0, dts = 590952620). [mpegts @ 01967ebfed00] Packet corrupt (stream = 0, dts = 590952620). [mpegts @ 01967ebfed00] stream 0 : no TS found at start of file, duration not set [mpegts @ 01967ebfed00] stream 1 : no TS found at start of file, duration not set Input #0, mpegts, from 'soc_udp_rx_02.ts': Duration: N/A, bitrate: N/A Program 1 Stream #0:0[0x1100]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 100 tbc Stream #0:1[0x1110]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 128 kb/s File 'testaudio.mp4' already exists. Overwrite? [y/N] y Output #0, mp4, to 'testaudio.mp4': Metadata: title : media source exentions encoder : Lavf58.47.100 Stream #0:0: Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 50 fps, 50 tbr, 90k tbn, 90k tbc Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s Stream mapping: Stream #0:0 -> #0:0 (copy) Stream #0:1 -> #0:1 (copy) Press [q] to stop, [?] for help [mpegts @ 01967ebfed00] Packet corrupt (stream = 0, dts = 590952620). frame= 902 fps=0.0 q=-1.0 Lsize=1803kB time=00:00:18.09 bitrate= 816.3kbits/s speed= 816x video:1469kB audio:277kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 3.293837% For although there it says aac (LC) if I run mp4info on the resultant file I get this: mp4info testaudio.mp4 File: major brand: iso5 minor version:200 compatible brand: iso5 compatible brand: iso6 compatible brand: mp41 fast start: yes Movie: duration: 0 ms time scale: 1000 fragments: yes Found 2 Tracks Track 1: flags:3 ENABLED IN-MOVIE id: 1 type: Video duration: 0 ms language: und media: sample count: 0 timescale:9 duration: 0 (media timescale units) duration: 0 (ms) bitrate (computed): 664.930 Kbps sample count with fragments: 902 duration with fragments: 1628337 duration with fragments: 18093 (ms) display width: 1280.00 display height: 720.00 Sample Description 0 Coding: avc1 (H.264) Width: 1280 Height: 720 Depth:
