Re: [FFmpeg-user] Wrong Channel count value on mp4a sample entry
Thanks Gyan. 2019년 2월 14일 (목) 오후 3:45에 Gyan 님이 작성: > > > On 14-02-2019 06:39 AM, Yuntaek Lim wrote: > > > > I could not find any constraints about channel count, cannot describe > greater > > than 2, for audioSampleEntry from iso 14496-12:2015. > > However, I've found "When values greater than 2 are used, the codec > > configuration should identify the channel assignment." > > The standard then goes on to say, > > "The audio output format (samplerate, samplesize and channelcount > fields) in the sample entry should be considered definitive only for > codecs that do not record their own output configuration. If the audio > codec has definitive information about the output format, it shall be > taken as definitive; in this case the samplerate, samplesize and > channelcount fields in the sample entry may be ignored, though sensible > values should be chosen (for example, the highest possible sampling rate)" > > For AAC, ASC is added from codec extradata, and provides the definitive > info. > > It may still be helpful to accurately record channel count for AAC, but > it's not required. > > Gyan > ___ > ffmpeg-user mailing list > ffmpeg-user@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Wrong Channel count value on mp4a sample entry
Hi Ted,
Thank you for your replying.
I want to make clear your explain.
> It is an old container format with varied history.
Do you mean "audioSampleEntry version 0" is old container?
> Many fields in iso container file boxes are just there to maintain
compatibility, and ignored & set to default value. In this case, the
channel count could only be 1 or 2, for mono and stereo. The default
happens to be 2.
I could not find any constraints about channel count, cannot describe greater
than 2, for audioSampleEntry from iso 14496-12:2015.
However, I've found "When values greater than 2 are used, the codec
configuration should identify the channel assignment."
I've found "Set to 1 for monaural sounds, 2 for stereo sounds. Higher
numbers of channels are not supported." from quick time format
specification. ("
https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP4939-CH205-75770
")
It may seem that 'mp4' can show channel count as 6, but 'mov' cannot be
described 6 channel count in the container. If it is right, I think,
"ffmpeg" describes channel_count in AudioSampleEntry as 6 for 5.1 channel.
Do you think my thought is right wrong?
2019년 2월 13일 (수) 오후 7:53에 Ted Park 님이 작성:
> > On Feb 12, 2019, at 12:49 AM, Yuntaek Lim wrote:
> >
> > I've created 5.1 channel aac-lc audio from 5.1 channel ac-3 audio.
> > However, the sample entry of "mp4a" box show channel_count as "2", not
> "6".
> > Howerver, the MPEG-4 elementary stream descriptor in "esds" box
> describes
> > channel count as 6.
>
> It is an old container format with varied history. Many fields in iso
> container file boxes are just there to maintain compatibility, and ignored
> & set to default value. In this case, the channel count could only be 1 or
> 2, for mono and stereo. The default happens to be 2.
> ___
> ffmpeg-user mailing list
> ffmpeg-user@ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email
> ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
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Re: [FFmpeg-user] Fast Conversion with compressed size and maintain Quality
Hi Amit, Do you have expected the minimum rate of reducing filesize and processing time? If you want maintain the quality, use low value of "crf" such as 18 to 20. The preset "ultrafast" provide fast encoding but lower compression rate. I suggest you decided the target filesize and the processing time. Then, you try to find the value of "crf" and the value of "preset" which satisfying you. "-i 503148_inn.mp4 -codec:a copy -preset ultrafast -vcodec h264 -crf 20 503148.mp4" Preset values are listed on "https://trac.ffmpeg.org/wiki/Encode/H.264;. Regards, 2019년 2월 13일 (수) 오전 3:29에 AMIT KUMAR 님이 작성: > Yes i have the original source file which is in .webm and then i am using > 503148.webm -preset ultrafast -max_muxing_queue_size 99 503148_inn.mp4 > After that mute video extracting audio and merge that audio file in one > that i have a audio file then we merge the audio and video then it creates > 503148_inn.mp4 which one i shared through link. > Then i need to compress, maintain quality and do that process fast. > > > On Tue, 12 Feb 2019 11:48 pm Ted Park > > Try to find the original source, I’m positive you are trying to work with > > a stream with many, many duplicated frames. > > ___ > > ffmpeg-user mailing list > > ffmpeg-user@ffmpeg.org > > http://ffmpeg.org/mailman/listinfo/ffmpeg-user > > > > To unsubscribe, visit link above, or email > > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". > ___ > ffmpeg-user mailing list > ffmpeg-user@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
[FFmpeg-user] Wrong Channel count value on mp4a sample entry
Hi, I've created 5.1 channel aac-lc audio from 5.1 channel ac-3 audio. However, the sample entry of "mp4a" box show channel_count as "2", not "6". Howerver, the MPEG-4 elementary stream descriptor in "esds" box describes channel count as 6. Command ffmpeg -loglevel debug -i source.mp4 -filter_complex "channelmap=map=FL-FL|FR-FR|FC-FC|LFE-LFE|SR-BR|SL-BL:channel_layout=5.1" -c:v copy -c:a libfdk_aac -profile:a aac_he -f mp4 demo.mp4 I've checked the channel_cout using " http://download.tsi.telecom-paristech.fr/gpac/mp4box.js/filereader.html;. I've checked the value of the "esds" box with shaka packager and ffrpobe. Can you explain the reason why the values are different, please? The source file "source.mp4" https://drive.google.com/open?id=0B2CC25n6pcNwejM1T3ZQb25hOENJS0xBTlhZcU1nZHZBOUM0 The output file "demo.mp4" https://drive.google.com/open?id=0B2CC25n6pcNwdnJNUmhQZU4wck1YRUhtVnRFekF1S2JnUU9z Regards, Yuntaek Lim ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
