[FFmpeg-devel] [PATCH] libvpx: ignore bitrate setting when -crf option is set.

James Zern jzern at google.com
Mon Dec 17 20:06:58 CET 2012


On Sat, Dec 15, 2012 at 5:03 PM, Clément Bœsch <ubitux at gmail.com> wrote:
> avctx->bit_rate is set by default, so unless you use -b:v 0, the CRF
> settings have no effect, and thus generally results in a pretty crappy
> quality output.
> ---
>  libavcodec/libvpxenc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/libvpxenc.c b/libavcodec/libvpxenc.c
> index 0de11b5..cdf9096 100644
> --- a/libavcodec/libvpxenc.c
> +++ b/libavcodec/libvpxenc.c
> @@ -271,7 +271,7 @@ static av_cold int vp8_init(AVCodecContext *avctx)
>      else if (ctx->crf)
>          enccfg.rc_end_usage = VPX_CQ;
>
> -    if (avctx->bit_rate) {
> +    if (avctx->bit_rate && enccfg.rc_end_usage != VPX_CQ) {

Unfortunately this doesn't work the same as e.g., x264/crf. In this
mode the target bitrate is actually used as a max, so if the codec
can't hit the quality it will fallback to vbr mode. Taking the default
would cause this to happen quite a bit on high resolution content.

>          enccfg.rc_target_bitrate = av_rescale_rnd(avctx->bit_rate, 1, 1000,
>                                                  AV_ROUND_NEAR_INF);
>      } else {
> --
> 1.8.0.2
>
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