MXF container does support PCM audio only?

[marcorocchini]

Hi

I'm a cat, please patience.

I wonder: I need to encode into mxf format something like this:

ffmpeg12ago2026.exe -i A025C098_260820JK_CANON.MXF -preset medium -c:v libx264 -x264-params 8x8dct=1 -g 33 -bf 2 -c:a ac3 -b:a 500k -ar 48000 -aspect 16:9 -flags +ilme+ildct -r 25 -vf setfield=tff OUT4_MXF_to_HD25interlacciatoFFMPEG12ago.MXF

but seems that audio codec accepted is only pcm, but if possible I need to encode to a compressed audio. Can I do this in a mxf container?!?

[ProWo]

but seems that audio codec accepted is only pcm

This is correct, pcm only.

[marcorocchini]

but I need to encode like aac or ac3 or mp3lame: why I cannot in mxf?

[jagabo]

According to the SMPTE spec MXF supports "MPEG encoded audio" (MPA? MP3?) as well as PCM.

https://pub.smpte.org/latest/st377-1/st377-1-2019.pdf

But ffmpeg's MXF muxer may not.

[marcorocchini]

But ffmpeg's MXF muxer may not.

[pandy]

So... what error is reported by ffmpeg if you trying to encode for example aac or even ac3 (consumer not professional codec) ?

[cholla]

I played around with this.
My answer is you have to use pcm only for audio in a .mxf container.
If a .mp4 container would work for you try this:

ffmpeg -i input.mxf -c:a ac3 -b:a 500k output.mp4

Or if you want to keep the video MPEG2:

ffmpeg -i input.mxf -c:v mpeg2video -b:v 5000k -maxrate 9000k -bufsize 1835k -c:a ac3 -b:a 500k output.mp4

[jagabo]

So... what error is reported by ffmpeg if you trying to encode for example aac or even ac3 (consumer not professional codec) ?

I don't remember the exact message, but something to the effect "muxer doesn't support that codec."

[cholla]

There are several errors in ffmpeg when doing this.
The one about .ac3 is this one:

Codec 'ac3' (86019) is not supported by the bitstream filter 'pcm_rechunk'. Supported codecs are: pcm_alaw (65543) pcm_f16le (65569) pcm_f24le (65570) pcm_f32be (65556) pcm_f32le (65557) pcm_f64be (65558) pcm_f64le (65559) pcm_mulaw (65542) pcm_s16be (65537) pcm_s16le (65536
) pcm_s24be (65549) pcm_s24daud (65552) pcm_s24le (65548) pcm_s32be (65545) pcm_s32le (65544) pcm_s64be (65568) pcm_s64le (65567) pcm_s8 (65540) pcm_sga (65572) pcm_u8 (65541) pcm_vidc (65571)

All supported codecs are pcm.

[pandy]

Accordingly to 'mxfenc.c': 'av_log(s, AV_LOG_ERROR, "Only pcm_s16le and pcm_s24le audio codecs are implemented\n");'

[cholla]

@ pandy,
What I posted was copied directly from the command prompt ffmpeg was trying to convert the .mxf file with.
I have never tried any pcm but pcm_s16le and pcm_s24le . Usually for conversion to .wav.
This was the error ffmpeg gave when trying to convert the audio in a .mxf file to .ac3 .
Keeping the format .mxf .
Give it a test & see what you get.