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.
>
>>
>>> + 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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