[FFmpeg-devel] [PATCH] AAC: Fix M/S stereo encoding

Michael Niedermayer michaelni at gmx.at
Tue Mar 3 14:07:00 CET 2015

On Tue, Mar 03, 2015 at 03:51:48AM -0300, Claudio Freire wrote:
> This patch fixes a pointer arithmetic bug in adjust_frame_information
> that resulted in heavily corrupted audio when using M/S encoding.
> Also, a backup copy of untransformed coefficients has to be kept
> around or attempts at re-processing the frame (which happens when
> hevavily overspending bits during transients) will result in
> re-encoding of the coefficients and subsequent corruption of the
> resulting stream.
> A/B testing shows the bug as corrected, but still cannot prove that
> M/S coding is a win at least in numbers. Limited listening tests do
> show improvement on M/S encoded samples in lower bitrates, but they're
> hidden among the other artifacts that remain to be corrected in the
> encoder.
> Some of the regressions flagged in the report do show poor stereo
> image (but not buggy), so M/S encoding is clearly not good enough yet
> to be defaulted to auto.
> In numbers, Patched against Unpatched, stereo_mode auto:




Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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