Anton Khirnov (12024-09-23):
> This way, av_buffersink_get_frame_flags() can replace almost all
> av_buffersink_get_*(), including some future parameters we will want to
> export.
> ---
> doc/APIchanges | 1 +
> libavfilter/buffersink.c | 47 ++++++++++++++++++++++++++++++++++++++++
> libavfilter/buffersink.h | 16 ++++++++++++--
> 3 files changed, 62 insertions(+), 2 deletions(-)
>
> diff --git a/doc/APIchanges b/doc/APIchanges
> index b392c756d7..5ddd7189f8 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -4,6 +4,7 @@ API changes, most recent first:
>
> 2024-09-xx - xxxxxxxxxx - lavfi 10.4.100
> Buffersink now sets AVFrame.time_base on the frames it outputs.
> + Add AV_BUFFERSINK_FLAG_PARAMS.
>
> 2024-09-23 - xxxxxxxxxx - lavc 61.18.100 - avcodec.h
> Add a new flag AV_CODEC_EXPORT_DATA_ENHANCEMENTS for export_side_data.
> diff --git a/libavfilter/buffersink.c b/libavfilter/buffersink.c
> index 575075ff47..d9cd074f17 100644
> --- a/libavfilter/buffersink.c
> +++ b/libavfilter/buffersink.c
> @@ -128,8 +128,55 @@ static int get_frame_internal(AVFilterContext *ctx,
> AVFrame *frame, int flags, i
> }
> }
>
> +static int get_frame_params(AVFilterContext *ctx, AVFrame *frame)
> +{
> + FilterLink *l = ff_filter_link(ctx->inputs[0]);
> + int ret = 0;
> +
> + frame->time_base = l->pub.time_base;
> + frame->format = l->pub.format;
> +
> + switch (l->pub.type) {
> + case AVMEDIA_TYPE_AUDIO:
> + ret = av_channel_layout_copy(&frame->ch_layout, &l->pub.ch_layout);
> + if (ret < 0)
> + goto fail;
> +
> + frame->sample_rate = l->pub.sample_rate;
> + break;
> + case AVMEDIA_TYPE_VIDEO:
> + frame->width = l->pub.w;
> + frame->height = l->pub.h;
> + frame->sample_aspect_ratio = l->pub.sample_aspect_ratio;
> + frame->colorspace = l->pub.colorspace;
> + frame->color_range = l->pub.color_range;
> + break;
> + default: av_assert0(0);
> + }
> +
> + if (l->hw_frames_ctx) {
> + frame->hw_frames_ctx = av_buffer_ref(l->hw_frames_ctx);
> + if (!frame->hw_frames_ctx) {
> + ret = AVERROR(ENOMEM);
> + goto fail;
> + }
> + }
> +
> + return 0;
> +fail:
> + av_frame_unref(frame);
> + return ret;
> +}
> +
> int attribute_align_arg av_buffersink_get_frame_flags(AVFilterContext *ctx,
> AVFrame *frame, int flags)
> {
> + if (flags & AV_BUFFERSINK_FLAG_PARAMS) {
> + if (flags & ~AV_BUFFERSINK_FLAG_PARAMS)
> + return AVERROR(EINVAL);
> +
> + return get_frame_params(ctx, frame);
> + }
> +
> return get_frame_internal(ctx, frame, flags,
> ff_filter_link(ctx->inputs[0])->min_samples);
> }
> diff --git a/libavfilter/buffersink.h b/libavfilter/buffersink.h
> index 361d603679..9c4468af5b 100644
> --- a/libavfilter/buffersink.h
> +++ b/libavfilter/buffersink.h
> @@ -87,14 +87,26 @@ int av_buffersink_get_frame_flags(AVFilterContext *ctx,
> AVFrame *frame, int flag
> * reference, but not remove it from the buffer. This is useful if you
> * need only to read a video/samples buffer, without to fetch it.
> */
> -#define AV_BUFFERSINK_FLAG_PEEK 1
> +#define AV_BUFFERSINK_FLAG_PEEK (1 << 0)
>
> /**
> * Tell av_buffersink_get_buffer_ref() not to request a frame from its input.
> * If a frame is already buffered, it is read (and removed from the buffer),
> * but if no frame is present, return AVERROR(EAGAIN).
> */
> -#define AV_BUFFERSINK_FLAG_NO_REQUEST 2
> +#define AV_BUFFERSINK_FLAG_NO_REQUEST (1 << 1)
> +
> +/**
> + * Retrieve stream parameters rather than frame data.
> + *
> + * When this flag is set, av_buffersink_get_frame_flags() fills the non-data
> + * fields of the supplied frame without causing any filtergraph activity.
> + *
> + * @note While frame data will be NULL, certain other allocated fields may be
> + * filled (e.g. ch_layout, hw_frames_ctx), so the frame should still be
> + * unreffed before reuse.
> + */
> +#define AV_BUFFERSINK_FLAG_PARAMS (1 << 2)
NAK, this is one of the worst API design I can think of for this task.
>
> /**
> * Set the frame size for an audio buffer sink.
--
Nicolas George
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