On 19.11.2017 17:39, Nicolas George wrote:
L'octidi 28 brumaire, an CCXXVI, Michael Roitzsch a écrit :
Hi FFmpeg team,
I was using af_pan to subtract one audio file from another. I first used an
amerge filter and then configured the pan filter with a channel formula like
c0=c0-c2|c1=c1-c3.
However, this does not work as expected. In debug output, I can see that
channel 0 correctly uses gain coefficients 1 and -1 for c0 and c2. But channel
1 incorrectly uses -1 and -1 for c1 and c3.
I looked into the code and found that the sign handling is currently wrong.
When the last contribution of a formula is subtracted, the sign variable will
be correctly set to -1 in line 191. But when then leaving the gains loop in
line 189, because we reached the end of the formula for an output channel, sign
is not reset. We therefore re-enter the gains loop for the next output channel
with sign still -1. The first gain in this new formula will therefore be
negated.
The attached patch fixes the problem for me.
Thanks, applied.
Would it be OK to backport the fix into release/3.4? I can do the
cherry-picking but am unsure about the policies and what other older
releases should possibly be adapted, too.
Regards,
Tobias
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