[FFmpeg-devel] [PATCH v2 3/4] avcodec/hevcdec: add nuh_layer_id option

[Zhao Zhili <quinkblack@foxmail.com>]

From: Zhao Zhili <zhilizhao@tencent.com>

It can be used to decode selected independent non-base layer. One
use case is alpha layer decoding.

Partially fix #7965.

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
---
 libavcodec/hevcdec.c | 56 +++++++++++++++++++++++++++++++++++++++++++-
 libavcodec/version.h |  2 +-
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 567e8d81d4..0b3d4e84d4 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -2956,6 +2956,35 @@ static int hevc_frame_end(HEVCContext *s)
     return 0;
 }
 
+static int check_layer(HEVCContext *s)
+{
+    const HEVCVPS *vps;
+
+    if (!s->nuh_layer_id)
+        return 0;
+
+    for (int i = 0; i < FF_ARRAY_ELEMS(s->ps.vps_list); i++) {
+        if (!s->ps.vps_list[i])
+            continue;
+
+        vps = (const HEVCVPS *)s->ps.vps_list[i]->data;
+        if (vps->vps_max_layers == 1) {
+            av_log(s->avctx, AV_LOG_ERROR,
+                    "Specified nuh_layer_id is %d but vps_max_layers is 1.\n",
+                    s->nuh_layer_id);
+            // Keep going for now.
+        } else if (s->nuh_layer_id > vps->vps_max_layer_id) {
+            av_log(s->avctx, AV_LOG_ERROR,
+                    "Specified nuh_layer_id is %d but vps_max_layer_id is %d.\n",
+                    s->nuh_layer_id, vps->vps_max_layer_id);
+            // It's a known issue that Apple videotoolbox encoder doesn't set
+            // vps_max_layer_id correctly. Keep going on purpose.
+        }
+    }
+
+    return 0;
+}
+
 static int decode_nal_unit(HEVCContext *s, const H2645NAL *nal)
 {
     HEVCLocalContext *lc = s->HEVClc;
@@ -2977,6 +3006,9 @@ static int decode_nal_unit(HEVCContext *s, const H2645NAL *nal)
                 goto fail;
         }
         ret = ff_hevc_decode_nal_vps(gb, s->avctx, &s->ps);
+        if (ret < 0)
+            goto fail;
+        ret = check_layer(s);
         if (ret < 0)
             goto fail;
         break;
@@ -3216,7 +3248,8 @@ static int decode_nal_units(HEVCContext *s, const uint8_t *buf, int length)
 
         if (s->avctx->skip_frame >= AVDISCARD_ALL ||
             (s->avctx->skip_frame >= AVDISCARD_NONREF
-            && ff_hevc_nal_is_nonref(nal->type)) || nal->nuh_layer_id > 0)
+            && ff_hevc_nal_is_nonref(nal->type)) ||
+            nal->nuh_layer_id != s->nuh_layer_id)
             continue;
 
         ret = decode_nal_unit(s, nal);
@@ -3315,6 +3348,10 @@ static int hevc_decode_extradata(HEVCContext *s, uint8_t *buf, int length, int f
     if (ret < 0)
         return ret;
 
+    ret = check_layer(s);
+    if (ret < 0)
+        return ret;
+
     /* export stream parameters from the first SPS */
     for (i = 0; i < FF_ARRAY_ELEMS(s->ps.sps_list); i++) {
         if (first && s->ps.sps_list[i]) {
@@ -3637,6 +3674,21 @@ static av_cold int hevc_decode_init(AVCodecContext *avctx)
     HEVCContext *s = avctx->priv_data;
     int ret;
 
+    if (s->nuh_layer_id > 0) {
+        if (avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {
+            av_log(avctx, AV_LOG_ERROR,
+                    "Decoding selected nuh_layer_id is under development. "
+                    "Use -strict experimental to use it anyway.\n");
+            return AVERROR(EINVAL);
+        }
+
+        if (avctx->hwaccel) {
+            av_log(avctx, AV_LOG_ERROR,
+                    "Decoding selected nuh_layer_id doesn't work with hwaccel.\n");
+            return AVERROR(EINVAL);
+        }
+    }
+
     if (avctx->active_thread_type & FF_THREAD_SLICE) {
         s->threads_number = avctx->thread_count;
         ret = ff_slice_thread_init_progress(avctx);
@@ -3691,6 +3743,8 @@ static const AVOption options[] = {
         AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, PAR },
     { "strict-displaywin", "stricly apply default display window size", OFFSET(apply_defdispwin),
         AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, PAR },
+    { "nuh_layer_id", "Select which nuh_layer_id to decode (only works with INBL)", OFFSET(nuh_layer_id),
+        AV_OPT_TYPE_INT,  {.i64 = 0}, 0, 62, PAR },
     { NULL },
 };
 
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 6b8a1dbb79..15f7c3fe3d 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -30,7 +30,7 @@
 #include "version_major.h"
 
 #define LIBAVCODEC_VERSION_MINOR  56
-#define LIBAVCODEC_VERSION_MICRO 100
+#define LIBAVCODEC_VERSION_MICRO 101
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \
-- 
2.25.1

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