[FFmpeg-devel] [PATCH v1] lavc/vaapi_encode_av1: Add qp option explicitly to set base q index

[Mark Thompson]

On 27/11/2023 00:58, fei.w.wang-at-intel.com at ffmpeg.org wrote:
> From: Fei Wang <fei.w.wang at intel.com>
> 
> Keep same way with librav1e/libsvtav1/qsv_av1.. to make it more
> acceptable instead of using global option "-global_quality".
> 
> Fix #10615
> 
> Signed-off-by: Fei Wang <fei.w.wang at intel.com>
> ---
>   doc/encoders.texi             | 1 +
>   libavcodec/vaapi_encode_av1.c | 6 ++++++
>   2 files changed, 7 insertions(+)
> 
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index 27a9acf076..2cffc32daf 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -4079,6 +4079,7 @@ Each encoder also has its own specific options:
>   @table @option
>   
>   @item av1_vaapi
> + at option{qp} sets the value of @emph{base_q_index}.
>   @option{profile} sets the value of @emph{seq_profile}.
>   @option{tier} sets the value of @emph{seq_tier}.
>   @option{level} sets the value of @emph{seq_level_idx}.
> diff --git a/libavcodec/vaapi_encode_av1.c b/libavcodec/vaapi_encode_av1.c
> index 5a9ff0f798..2e327fec5a 100644
> --- a/libavcodec/vaapi_encode_av1.c
> +++ b/libavcodec/vaapi_encode_av1.c
> @@ -79,6 +79,7 @@ typedef struct VAAPIEncodeAV1Context {
>       int cdef_param_size;
>   
>       /** user options */
> +    int qp;
>       int profile;
>       int level;
>       int tier;
> @@ -786,6 +787,9 @@ static av_cold int vaapi_encode_av1_init(AVCodecContext *avctx)
>           return AVERROR(EINVAL);
>       }
>   
> +    if (priv->qp > 0)
> +        ctx->explicit_qp = priv->qp;
> +
>       ret = ff_vaapi_encode_init(avctx);
>       if (ret < 0)
>           return ret;
> @@ -864,6 +868,8 @@ static av_cold int vaapi_encode_av1_close(AVCodecContext *avctx)
>   static const AVOption vaapi_encode_av1_options[] = {
>       VAAPI_ENCODE_COMMON_OPTIONS,
>       VAAPI_ENCODE_RC_OPTIONS,
> +    { "qp", "Base q index (for P-frames; scaled by qfactor/qoffset for I/B)",
> +      OFFSET(qp), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 255, FLAGS },
>       { "profile", "Set profile (seq_profile)",
>         OFFSET(profile), AV_OPT_TYPE_INT,
>         { .i64 = AV_PROFILE_UNKNOWN }, AV_PROFILE_UNKNOWN, 0xff, FLAGS, "profile" },

Disagree; QP is not a concept in AV1.  Further, your examples from other encoders do not have a consistent view of what it should mean.

librav1e.c:

     { "qp", "use constant quantizer mode", OFFSET(quantizer), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 255, VE },

0-255 is presumably the base_q_idx scale.

libsvtav1.c:

     { "qp", "Initial Quantizer level value", OFFSET(qp),      AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 63, VE },

0-63 is presumably the H.26x-qp-ish scale used by some VP9/AV1 encoders which maps nonlinearly to the internal scale.

qsv_av1 doesn't seem to have such an option.

Thanks,

- Mark