Re: [FFmpeg-devel] [PATCH v7 3/4] avcodec/hevc: Add alpha layer support

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Zhao Zhili:
> From: Zhao Zhili <zhilizhao@tencent.com>
> 
> Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
> ---
>  libavcodec/hevc/hevcdec.c | 73 ++++++++++++++++++++++++++++++++++++++-
>  libavcodec/hevc/hevcdec.h |  2 ++
>  libavcodec/hevc/refs.c    | 35 ++++++++++++++++++-
>  3 files changed, 108 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/hevc/hevcdec.c b/libavcodec/hevc/hevcdec.c
> index e9c045f7a1..f71edf213b 100644
> --- a/libavcodec/hevc/hevcdec.c
> +++ b/libavcodec/hevc/hevcdec.c
> @@ -466,6 +466,25 @@ static int export_multilayer(HEVCContext *s, const HEVCVPS *vps)
>      return 0;
>  }
>  
> +int ff_hevc_is_alpha_video(const HEVCContext *s)
> +{
> +    const HEVCVPS *vps = s->vps;
> +    int ret = 0;
> +
> +    if (vps->nb_layers != 2 || !vps->layer_id_in_nuh[1])
> +        return 0;
> +
> +    /* decode_vps_ext() guarantees that SCALABILITY_AUXILIARY with AuxId other
> +     * than alpha cannot reach here.
> +     */
> +    ret = (s->vps->scalability_mask_flag & HEVC_SCALABILITY_AUXILIARY);
> +
> +    av_log(s->avctx, AV_LOG_DEBUG, "Multi layer video, %s alpha video\n",
> +           ret ? "is" : "not");
> +
> +    return ret;
> +}
> +
>  static int setup_multilayer(HEVCContext *s, const HEVCVPS *vps)
>  {
>      unsigned layers_active_output = 0, highest_layer;
> @@ -473,6 +492,18 @@ static int setup_multilayer(HEVCContext *s, const HEVCVPS *vps)
>      s->layers_active_output = 1;
>      s->layers_active_decode = 1;
>  
> +    if (ff_hevc_is_alpha_video(s)) {
> +        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
> +
> +        if (!(desc->flags & AV_PIX_FMT_FLAG_ALPHA))
> +            return 0;
> +
> +        s->layers_active_decode = (1 << vps->nb_layers) - 1;
> +        s->layers_active_output = 1;
> +
> +        return 0;
> +    }
> +
>      // nothing requested - decode base layer only
>      if (!s->nb_view_ids)
>          return 0;
> @@ -530,6 +561,34 @@ static int setup_multilayer(HEVCContext *s, const HEVCVPS *vps)
>      return 0;
>  }
>  
> +static enum AVPixelFormat map_to_alpha_format(HEVCContext *s,
> +                                              enum AVPixelFormat pix_fmt)
> +{
> +    switch (pix_fmt) {
> +    case AV_PIX_FMT_YUV420P:
> +    case AV_PIX_FMT_YUVJ420P:
> +        return AV_PIX_FMT_YUVA420P;
> +    case AV_PIX_FMT_YUV420P10:
> +        return AV_PIX_FMT_YUVA420P10;
> +    case AV_PIX_FMT_YUV444P:
> +        return AV_PIX_FMT_YUVA444P;
> +    case AV_PIX_FMT_YUV422P:
> +        return AV_PIX_FMT_YUVA422P;
> +    case AV_PIX_FMT_YUV422P10LE:
> +        return AV_PIX_FMT_YUVA422P10LE;
> +    case AV_PIX_FMT_YUV444P10:
> +        return AV_PIX_FMT_YUVA444P10;
> +    case AV_PIX_FMT_YUV444P12:
> +        return AV_PIX_FMT_YUVA444P12;
> +    case AV_PIX_FMT_YUV422P12:
> +        return AV_PIX_FMT_YUVA422P12;
> +    default:
> +        av_log(s->avctx, AV_LOG_WARNING, "No alpha pixel format map for %s\n",
> +               av_get_pix_fmt_name(pix_fmt));
> +        return AV_PIX_FMT_NONE;
> +    }
> +}
> +
>  static enum AVPixelFormat get_format(HEVCContext *s, const HEVCSPS *sps)
>  {
>  #define HWACCEL_MAX (CONFIG_HEVC_DXVA2_HWACCEL + \
> @@ -540,9 +599,13 @@ static enum AVPixelFormat get_format(HEVCContext *s, const HEVCSPS *sps)
>                       CONFIG_HEVC_VIDEOTOOLBOX_HWACCEL + \
>                       CONFIG_HEVC_VDPAU_HWACCEL + \
>                       CONFIG_HEVC_VULKAN_HWACCEL)
> -    enum AVPixelFormat pix_fmts[HWACCEL_MAX + 2], *fmt = pix_fmts;
> +    enum AVPixelFormat pix_fmts[HWACCEL_MAX + 3], *fmt = pix_fmts;
> +    enum AVPixelFormat alpha_fmt = AV_PIX_FMT_NONE;
>      int ret;
>  
> +    if (ff_hevc_is_alpha_video(s))
> +        alpha_fmt = map_to_alpha_format(s, sps->pix_fmt);
> +
>      switch (sps->pix_fmt) {
>      case AV_PIX_FMT_YUV420P:
>      case AV_PIX_FMT_YUVJ420P:
> @@ -664,6 +727,8 @@ static enum AVPixelFormat get_format(HEVCContext *s, const HEVCSPS *sps)
>          break;
>      }
>  
> +    if (alpha_fmt != AV_PIX_FMT_NONE)
> +        *fmt++ = alpha_fmt;
>      *fmt++ = sps->pix_fmt;
>      *fmt = AV_PIX_FMT_NONE;
>  
> @@ -3194,6 +3259,12 @@ static int hevc_frame_start(HEVCContext *s, HEVCLayerContext *l,
>                  !sps->vui.common.video_signal_type_present_flag)
>                  pix_fmt = sps_base->pix_fmt;
>  
> +            // Ignore range mismatch between base layer and alpha layer
> +            if (ff_hevc_is_alpha_video(s) &&
> +                sps_base->pix_fmt == AV_PIX_FMT_YUV420P &&
> +                pix_fmt == AV_PIX_FMT_YUVJ420P)
> +                pix_fmt = sps_base->pix_fmt;
> +
>              if (pix_fmt     != sps_base->pix_fmt ||
>                  sps->width  != sps_base->width   ||
>                  sps->height != sps_base->height) {
> diff --git a/libavcodec/hevc/hevcdec.h b/libavcodec/hevc/hevcdec.h
> index 4e95035688..b2b725b5cd 100644
> --- a/libavcodec/hevc/hevcdec.h
> +++ b/libavcodec/hevc/hevcdec.h
> @@ -714,6 +714,8 @@ void ff_hevc_hls_residual_coding(HEVCLocalContext *lc, const HEVCPPS *pps,
>  
>  void ff_hevc_hls_mvd_coding(HEVCLocalContext *lc, int x0, int y0, int log2_cb_size);
>  
> +int ff_hevc_is_alpha_video(const HEVCContext *s);
> +
>  extern const uint8_t ff_hevc_qpel_extra_before[4];
>  extern const uint8_t ff_hevc_qpel_extra_after[4];
>  extern const uint8_t ff_hevc_qpel_extra[4];
> diff --git a/libavcodec/hevc/refs.c b/libavcodec/hevc/refs.c
> index dd7f7f95a8..6f10efd0ac 100644
> --- a/libavcodec/hevc/refs.c
> +++ b/libavcodec/hevc/refs.c
> @@ -79,6 +79,31 @@ void ff_hevc_flush_dpb(HEVCContext *s)
>      }
>  }
>  
> +static int replace_alpha_plane(AVFrame *alpha, AVFrame *base)
> +{
> +    AVBufferRef *base_a = av_frame_get_plane_buffer(base, 3);
> +    uintptr_t data = (uintptr_t)alpha->data[0];
> +    int ret;
> +
> +    for (int i = 0; i < FF_ARRAY_ELEMS(alpha->buf) && alpha->buf[i]; i++) {
> +        AVBufferRef *buf = alpha->buf[i];
> +        uintptr_t buf_begin = (uintptr_t)buf->data;
> +
> +        if (data >=  buf_begin && data < buf_begin + buf->size) {
> +            ret = av_buffer_replace(&alpha->buf[i], base_a);
> +            if (ret < 0)
> +                return ret;
> +
> +            alpha->linesize[0] = base->linesize[3];
> +            alpha->data[0] = base->data[3];
> +
> +            return 0;
> +        }
> +    }

Why does the decoding process actually need multiple references to the
buffer of the alpha plane?

> +
> +    return AVERROR_BUG;
> +}
> +
>  static HEVCFrame *alloc_frame(HEVCContext *s, HEVCLayerContext *l)
>  {
>      const HEVCVPS *vps = l->sps->vps;
> @@ -103,7 +128,7 @@ static HEVCFrame *alloc_frame(HEVCContext *s, HEVCLayerContext *l)
>          }
>  
>          // add view ID side data if it's nontrivial
> -        if (vps->nb_layers > 1 || view_id) {
> +        if (!ff_hevc_is_alpha_video(s) && (vps->nb_layers > 1 || view_id)) {
>              HEVCSEITDRDI *tdrdi = &s->sei.tdrdi;
>              AVFrameSideData *sd = av_frame_side_data_new(&frame->f->side_data,
>                                                           &frame->f->nb_side_data,
> @@ -161,7 +186,15 @@ static HEVCFrame *alloc_frame(HEVCContext *s, HEVCLayerContext *l)
>          if (ret < 0)
>              goto fail;
>  
> +
>          frame->pps = av_refstruct_ref_c(s->pps);
> +        if (l != &s->layers[0] && ff_hevc_is_alpha_video(s)) {
> +            AVFrame *alpha = frame->f;
> +            AVFrame *base = s->layers[0].cur_frame->f;
> +            ret = replace_alpha_plane(alpha, base);
> +            if (ret < 0)
> +                goto fail;
> +        }
>  
>          return frame;
>  fail:

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