On Tue, Jul 28, 2020 at 3:30 PM Takio Yamaoka <y.ta...@gmail.com> wrote:
>
> An initial value of `AVCodecContext::chromaoffset` is zero,
> then it causes to block `-chromaoffset` setting as result.
> In addition, even though a negative number of `chromaoffset`
> is meaningful, `X264Context::chroma_offset` is initialized
> with `-1` as no setting and ignored if it is negative number.
>
> To fix above, it changes ...
> - a value of `X264Context::chroma_offset` to 0 as no setting
> - due to x264's default value
> - conditional statement to import `-chromaoffset`
>
> Signed-off-by: Takio Yamaoka <y.ta...@gmail.com>
> ---
> libavcodec/libx264.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
> index 7bbeab7d4c..347d29df27 100644
> --- a/libavcodec/libx264.c
> +++ b/libavcodec/libx264.c
> @@ -681,11 +681,11 @@ static av_cold int X264_init(AVCodecContext *avctx)
>
> #if FF_API_PRIVATE_OPT
> FF_DISABLE_DEPRECATION_WARNINGS
> - if (avctx->chromaoffset >= 0)
> + if (avctx->chromaoffset)
> x4->chroma_offset = avctx->chromaoffset;
> FF_ENABLE_DEPRECATION_WARNINGS
> #endif
> - if (x4->chroma_offset >= 0)
> + if (x4->chroma_offset)
> x4->params.analyse.i_chroma_qp_offset = x4->chroma_offset;
>
> if (avctx->gop_size >= 0)
> @@ -1140,7 +1140,7 @@ static const AVOption options[] = {
> { "vlc", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = 0 },
> INT_MIN, INT_MAX, VE, "coder" },
> { "ac", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = 1 },
> INT_MIN, INT_MAX, VE, "coder" },
> { "b_strategy", "Strategy to choose between I/P/B-frames",
> OFFSET(b_frame_strategy), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 2, VE },
> - { "chromaoffset", "QP difference between chroma and luma",
> OFFSET(chroma_offset), AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX, VE },
> + { "chromaoffset", "QP difference between chroma and luma",
> OFFSET(chroma_offset), AV_OPT_TYPE_INT, { .i64 = 0 }, INT_MIN, INT_MAX, VE },
> { "sc_threshold", "Scene change threshold",
> OFFSET(scenechange_threshold), AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN,
> INT_MAX, VE },
> { "noise_reduction", "Noise reduction",
> OFFSET(noise_reduction), AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX, VE
> },
>
General change looks alright to me, after checking the following points.
- AVCodecContext's chromaoffset indeed defaults to 0 through the
DEFAULT define (#define DEFAULT 0 //should be NAN but it does not work
as it is not a constant in glibc as required by ANSI/ISO C)
- x264 default is 0 (thus we thankfully haven't overwritten this
before, and the patch doesn't lead to a change in that behavior,
either)
- value in x264 can be between -12 and 12, thus both positive and
negative values indeed can be set
(x264_clip3(h->param.analyse.i_chroma_qp_offset, -12, 12) can be found
in x264's code)
Best regards,
Jan
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
