On 2 December 2017 at 17:46, Andrew D'Addesio <modchip...@gmail.com> wrote:
> When decoding to downmixed mono, don't put the channels out of phase,
> as they will cancel out and create audible artifacts. (See
> RFC 8251 sec. 10.)
>
> Signed-off-by: Andrew D'Addesio <modchip...@gmail.com>
> ---
> libavcodec/opus_pvq.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/libavcodec/opus_pvq.c b/libavcodec/opus_pvq.c
> index 2f7aa74..f18c010 100644
> --- a/libavcodec/opus_pvq.c
> +++ b/libavcodec/opus_pvq.c
> @@ -643,7 +643,13 @@ static av_always_inline uint32_t
> quant_band_template(CeltPVQ *pvq, CeltFrame *f,
> }
> } else {
> inv = (b > 2 << 3 && f->remaining2 > 2 << 3) ?
> ff_opus_rc_dec_log(rc, 2) : 0;
> +
> + /* Don't put the channels out of phase if we are decoding
> to downmixed
> + * mono as this subjectively sounds bad (RFC 8251 section
> 10). */
> + if (f->channels == 1)
> + inv = 0;
> }
> +
> itheta = 0;
> }
> qalloc = opus_rc_tell_frac(rc) - tell;
> --
> 2.15.1.windows.2
>
> _______________________________________________
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> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
RFC8251 made this optional, pushed a new version which added an option to
toggle this.
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