> On Feb 11, 2025, at 20:12, Andreas Rheinhardt
> <andreas.rheinha...@outlook.com> wrote:
>
> Zhao Zhili:
>>
>>
>>> On Feb 11, 2025, at 19:23, Andreas Rheinhardt
>>> <andreas.rheinha...@outlook.com> wrote:
>>>
>>> Zhao Zhili:
>>>> From: Zhao Zhili <zhiliz...@tencent.com>
>>>>
>>>> Signed-off-by: Zhao Zhili <zhiliz...@tencent.com>
>>>> ---
>>>> libavcodec/hevc/hevcdec.c | 73 ++++++++++++++++++++++++++++++++++++++-
>>>> libavcodec/hevc/hevcdec.h | 2 ++
>>>> libavcodec/hevc/refs.c | 34 +++++++++++++++++-
>>>> 3 files changed, 107 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..da0bac8d9c 100644
>>>> --- a/libavcodec/hevc/refs.c
>>>> +++ b/libavcodec/hevc/refs.c
>>>> @@ -79,6 +79,30 @@ 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);
>>>> + uint8_t *data = alpha->data[0];
>>>> + int ret;
>>>> +
>>>> + for (int i = 0; i < FF_ARRAY_ELEMS(alpha->buf) && alpha->buf[i]; i++)
>>>> {
>>>> + AVBufferRef *buf = alpha->buf[i];
>>>> +
>>>> + if (data >= buf->data && data < buf->data + buf->size) {
>>>
>>> Pointer comparisons (other than equality/inquality comparisons) are
>>> undefined behavior unless the two pointers point into the same array (or
>>> one past the last element of an array).
>>
>> av_frame_get_plane_buffer does the same compare. Any idea to fix this UB?
>
> ISO C does not have a portable way to achieve this (except iterating
> over buf->data[0..buf->size] and checking via ==).
> In practice (in a flat memory space) casting to uintptr_t should work.
What’s the difference with and without cast in practice?
>
>>
>>>
>>>> + 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;
>>>> + }
>>>> + }
>>>> +
>>>> + return AVERROR_BUG;
>>>> +}
>>>> +
>>>> static HEVCFrame *alloc_frame(HEVCContext *s, HEVCLayerContext *l)
>>>> {
>>>> const HEVCVPS *vps = l->sps->vps;
>>>> @@ -103,7 +127,7 @@ 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 +185,15 @@ 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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