AudioFrame with planar channel layout creates wrong number of planes

[MacJudge]

Consider the following code:

import av
for channels in range(1, 25):
    for sample_format in av.audio.frame.format_dtypes.keys():
        frame = av.AudioFrame(format=sample_format, layout=str(channels) + 'C', samples=1)
        if (sample_format[-1] != 'p' and len(frame.planes) != 1) or (sample_format[-1] == 'p' and len(frame.planes) != channels):
            print(f"{sample_format}: {frame.layout.nb_channels} {len(frame.planes)}")

The expected outcome would be, that everything runs fine without printing anything.

In my case (PyAV 14.3.0, FFmpeg 7.1.1, Python 3.11.11, Debian based Linux) for all planar sample formats with more than 7 channels a line is printed. For 8 channels there are always 9 planes and for more than 8 channels the number of planes seems to be a random number >= number of channels (so it might just print no line by accident, but usually there are more planes than expected). The code uses just one sample and should run without problems, but with increasing number of channels or number of samples this will always crash the Python interpreter.

I think the reason for this bug is, that additional pointers for planar sample formats allocated by avcodec_fill_audio_frame are not handled correctly. [1]

In case this is considered just an academic bug: I tried to load an OGG Vorbis file with 8 channels and Python always crashed because of this.

PS: I'm iterating over all defined sample formats in format_dtypes and I think this dictionary needs an update, as there are additional sample formats for 64 bit signed integers (s64 and s64p) supported by libav since version 4. [2]

[1] https://ffmpeg.org/doxygen/7.0/libavcodec_2utils_8c_source.html#l00369
[2] https://ffmpeg.org/doxygen/7.0/samplefmt_8h_source.html#l00055