On 1/13/2025 5:30 PM, Michael Niedermayer wrote:
HiOn Mon, Jan 13, 2025 at 03:51:07PM -0300, James Almer wrote:On 1/13/2025 12:49 AM, Michael Niedermayer wrote:Hi James On Sun, Jan 12, 2025 at 06:52:55PM -0300, James Almer wrote:On 1/12/2025 6:25 PM, Michael Niedermayer wrote:Hi On Sat, Jan 11, 2025 at 11:13:30AM -0300, James Almer wrote:With this, the output from ffmpeg -i $fate-samples/ac3/monsters_inc_5.1_448_small.ac3 -af aresample,aformat=channel_layouts=mono -f s16le - matches the one from ffmpeg -downmix mono -i $fate-samples/ac3/monsters_inc_5.1_448_small.ac3 -f s16le - When testing with tiny_psnr. Signed-off-by: James Almer <jamr...@gmail.com> --- libswresample/rematrix.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)This worsense test results:What test is this, and how is it read?its just tests/swresample and a dumb script that tries to compare its output to spot cases that worsenIs this any better? (Also makes the above command line match)Can we take a step back here. please explain what you are fixing exactly the matrix should be 1.0 on channels that exist before and afterwards so a speaker thats there before the mix and after the mix produces the same sound. That should naively be closest to correct, Speakers which disappear need to have their sound mixed into existing speakers. But existing speakers that dont change should not have their output change if the goal is to replicate the input Of course maybe something else is better in some case (i dont know) but id like to read an explanation what and why. Not just that it matches something else
The line in question is the coeff to mix front center from input to front center from output in case front L/R channels from input are also mixed into front center (so surround/3.1 -> mono, 5.1 -> mono, etc).
The current coeff doesn't match the behavior of the downmix code in the ac3 decoder. Seeing it's the only coeff here where the value is outright overwritten rather than being subtracted/added, it's probably bogus, and I'm trying to find the (most) correct one that gives equal results.
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