Thanks for the explanation Nicolas. When the matrix is not explicitly provided, lswr computes it. For that, > it needs the channel layout, because you do not mix a rear channel the > same way as a subwoofer. This patch absolutely needs to be tested under > these circumstances too. >
This patch does not affect the behavior when the downmix matrix is not explicitly provided. For example, running: ./ffmpeg -i input_9ch.wav -ac 6 output_6ch.wav Results in: [auto_resampler_0 @ 0x5617a8668c80] [SWR @ 0x5617a8669180] Rematrix is needed between 9 channels and 5.1 but there is not enough information to do it [auto_resampler_0 @ 0x5617a8668c80] Failed to configure output pad on auto_resampler_0 Which I think is a reasonable expectation. Since the channel layout for 9 channel audio is undefined, there is no 'standard' way to downmix it to 5.1 or 2.0 etc. For 'known' channel layouts, the output is correct as well: ./ffmpeg -i input_8ch.wav -ac 6 output_6ch.wav [auto_resampler_0 @ 0x55adfbd6fa00] [SWR @ 0x55adfbd6fec0] FL: FL:0.585786 FR:0.000000 FC:0.000000 LFE:0.000000 BL:0.000000 BR:0.000000 SL:0.000000 SR:0.000000 [auto_resampler_0 @ 0x55adfbd6fa00] [SWR @ 0x55adfbd6fec0] FR: FL:0.000000 FR:0.585786 FC:0.000000 LFE:0.000000 BL:0.000000 BR:0.000000 SL:0.000000 SR:0.000000 [auto_resampler_0 @ 0x55adfbd6fa00] [SWR @ 0x55adfbd6fec0] FC: FL:0.000000 FR:0.000000 FC:0.585786 LFE:0.000000 BL:0.000000 BR:0.000000 SL:0.000000 SR:0.000000 [auto_resampler_0 @ 0x55adfbd6fa00] [SWR @ 0x55adfbd6fec0] LFE: FL:0.000000 FR:0.000000 FC:0.000000 LFE:0.585786 BL:0.000000 BR:0.000000 SL:0.000000 SR:0.000000 [auto_resampler_0 @ 0x55adfbd6fa00] [SWR @ 0x55adfbd6fec0] BL: FL:0.000000 FR:0.000000 FC:0.000000 LFE:0.000000 BL:0.585786 BR:0.000000 SL:0.414214 SR:0.000000 [auto_resampler_0 @ 0x55adfbd6fa00] [SWR @ 0x55adfbd6fec0] BR: FL:0.000000 FR:0.000000 FC:0.000000 LFE:0.000000 BL:0.000000 BR:0.585786 SL:0.000000 SR:0.414214 [auto_resampler_0 @ 0x55adfbd6fa00] ch:8 chl:7.1 fmt:s16 r:48000Hz -> ch:6 chl:5.1 fmt:s16 r:48000Hz Thank you for raising that point and please let me know if you still have concerns. Regards, -- Marcin Gorzel | Software Engineer | gor...@google.com | _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel