[FFmpeg-devel] [PATCH V3] avcodec/libvpxenc: add ROI-based encoding support for VP8/VP9 support

[James Zern]

Hi,

On Tue, Aug 13, 2019 at 8:29 PM Guo, Yejun <yejun.guo at intel.com> wrote:
> example command line to verify it:
> ./ffmpeg -i input.stream -vf addroi=0:0:iw/3:ih/3:-0.8 -c:v libvpx -b:v 2M tmp.webm
>
> Signed-off-by: Guo, Yejun <yejun.guo at intel.com>
> ---
>  libavcodec/libvpxenc.c | 197 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 197 insertions(+)
>
> [...]
>
> +
> +    memset(roi_map, 0, sizeof(*roi_map));
> +
> +    /* segment id 0 in roi_map is reserved for the areas not covered by AVRegionOfInterest.
> +     * segment id 0 in roi_map is also for the areas with AVRegionOfInterest.qoffset near 0.
> +     * (delta_q of segment id 0 is 0).
> +     */
> +    segment_mapping[MAX_DELTA_Q] = 1;
> +    /* roi_map has memset with zero, just explictly set it again for explict understanding. */

There are some typos in this, but as the comment says, it's redundant.
I think this and
the next line could be removed.

> +    roi_map->delta_q[0] = 0;
> +    segment_id = 1;
> +
> +    roi = (const AVRegionOfInterest*)sd->data;
> +    self_size = roi->self_size;
> +    if (!self_size || sd->size % self_size != 0) {
> +        av_log(avctx, AV_LOG_ERROR, "Invalid AVRegionOfInterest.self_size.\n");
> +        return AVERROR(EINVAL);
> +    }
> +    nb_rois = sd->size / self_size;
> +
> +    /* This list must be iterated from zero because regions are
> +     * defined in order of decreasing importance. So discard less
> +     * important areas if they exceed the segment count.
> +     */
> +    for (int i = 0; i < nb_rois; i++) {
> +        int delta_q;
> +        int mapping_index;
> +
> +        roi = (const AVRegionOfInterest*)(sd->data + self_size * i);
> +        if (roi->qoffset.den == 0) {
> +            av_log(avctx, AV_LOG_ERROR, "AVRegionOfInterest.qoffset.den must not be zero.\n");
> +            return AVERROR(EINVAL);
> +        }
> +
> +        delta_q = (int)(roi->qoffset.num * 1.0f / roi->qoffset.den * MAX_DELTA_Q);
> +        delta_q = av_clip(delta_q, -MAX_DELTA_Q, MAX_DELTA_Q);
> +

Note that libvpx allows other adjustments (loop filter, block skipping, among
others), but there may not be a way to provide this with AVRegionOfInterest.

> [...]
> +
> +        if (ctx->aq_mode > 0 || ctx->cpu_used < 5 || ctx->deadline != VPX_DL_REALTIME) {
> +            if (!ctx->roi_warned) {
> +                ctx->roi_warned = 1;
> +                if (ctx->aq_mode > 0)
> +                    av_log(avctx, AV_LOG_WARNING, "ROI is disabled when any of AQ mode is on, skipping ROI.\n");
> +                else
> +                    av_log(avctx, AV_LOG_WARNING, "due to libvpx's internal issue (see function apply_roi_map), skipping ROI.\n");

I think this could just mention that ROI is only supported with aq_mode==0,
cpu_used >= 5 and deadline set to realtime rather than having a more specific
statement like this one.