why don't work old batch ffmpeg extraestereo command in new version?

Question

I use this batch command for years in ffmpeg, but from update to the last version don't work and don't see in documentation whats the problem.

ffmpeg -i C:\Pelis\video.mkv -vcodec copy -map 0:a -map 0:v -acodec aac -b:a 384k -ac 2 -filter_complex extrastereo C:\Pelis\Salida.mkv

I recive that error allways:

[fc#0 @ 000001c68f377180] Cannot find a matching stream for unlabeled input pad extrastereo:default Error binding filtergraph inputs/outputs: Invalid argument

Answer 1

It is not working due to the audio mapping: -map 0:a.

The following command should work:
ffmpeg -i C:\Pelis\video.mkv -vcodec copy -acodec aac -b:a 384k -ac 2 -filter_complex extrastereo C:\Pelis\Salida.mkv

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It looks like the behavior of "unlabeled input" to a filter was changed between FFmpeg versions (say between version 5.xx and version 7.0).

• Example for "unlabeled input": -filter_complex extrastereo.
• Example for "labeled input": -filter_complex [0:a]extrastereo.

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-map 0:a maps the original audio stream of the input, to the output.
-filter_complex extrastereo looks (automatically) for some default input audio stream, and creates a new audio output stream.
Now we have to candidate output audio streams...

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There is a different behavior of FFmpeg version 5.xx and version 7.0:

• FFmpeg 5.xx ignores the -map 0:a, and maps the output of extrastereo to Salida.mkv.
• FFmpeg 7.0 maps the original input stream 0:a to Salida.mkv, and refuses to (automatically) select it as input to extrastereo filter.

The correct behavior is undefined, and it is a good practice to explicitly define the input to each filter: [0:a]extrastereo.

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Note that using both -map 0:a and "[0:a]extrastereo[audio]" -map 0:v -map [audio] as suggested by Ricardo: ffmpeg -i C:\Pelis\video.mkv -vcodec copy -map 0:a -map 0:v -acodec aac -b:a 384k -ac 2 -filter_complex "[0:a]extrastereo[audio]" -map 0:v -map [audio] C:\Pelis\Salida.mkv, creates an output with two audio streams.
I assume your intention is creating an output with one audio streams.

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Note:
FFmpeg 6.1 has a different behavior than both FFmpeg 5 and FFmpeg 7.
When using the original command with FFmpeg 6.1, the output has two audio streams.
Mapping the original audio due to -map 0:a, and also mapping the output of extrastereo, seems to be the correct behavior.
I suppose that FFmpeg 5 and earlier versions have a bug, the bug was fixed in FFmpeg 6, and with FFmpeg 7 there is an error message (giving error message is probably for the best).