[FFmpeg-devel] [PATCH] Allow enabling SVC in libaomenc

[Chun-Min Chang]

This patch updates libaomenc.c to accept parameters for SVC (Scalable
Video Coding) settings via the FFmpeg API `av_opt_set`. The SVC
configuration is applied based on the provided parameters. As libaom's
SVC functionality only operates with constant bitrate encoding [1],
these parameters will only take effect when the bitrate is set to
constant.

[1] 
https://aomedia.googlesource.com/aom/+/a7ef80c44bfb34b08254194b1ab72d4e93ff4b07/av1/encoder/svc_layercontext.h#115

Signed-off-by: Chun-Min Chang <chun.m.chang at gmail.com>
---
  libavcodec/libaomenc.c | 75 ++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 75 insertions(+)

diff --git a/libavcodec/libaomenc.c b/libavcodec/libaomenc.c
index dec74ebecd..a8602a6b56 100644
--- a/libavcodec/libaomenc.c
+++ b/libavcodec/libaomenc.c
@@ -30,6 +30,7 @@
  #include <aom/aomcx.h>
   #include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
  #include "libavutil/base64.h"
  #include "libavutil/common.h"
  #include "libavutil/cpu.h"
@@ -137,6 +138,7 @@ typedef struct AOMEncoderContext {
      int enable_diff_wtd_comp;
      int enable_dist_wtd_comp;
      int enable_dual_filter;
+    AVDictionary *svc_parameters;
      AVDictionary *aom_params;
  } AOMContext;
  @@ -201,6 +203,7 @@ static const char *const ctlidstr[] = {
      [AV1E_GET_TARGET_SEQ_LEVEL_IDX]     = "AV1E_GET_TARGET_SEQ_LEVEL_IDX",
  #endif
      [AV1_GET_NEW_FRAME_IMAGE]           = "AV1_GET_NEW_FRAME_IMAGE",
+    [AV1E_SET_SVC_PARAMS]               = "AV1E_SET_SVC_PARAMS",
  };
   static av_cold void log_encoder_error(AVCodecContext *avctx, const 
char *desc)
@@ -382,6 +385,31 @@ static av_cold int codecctl_imgp(AVCodecContext *avctx,
      return 0;
  }
  +static av_cold int codecctl_svcp(AVCodecContext *avctx,
+#ifdef UENUM1BYTE
+                                 aome_enc_control_id id,
+#else
+                                 enum aome_enc_control_id id,
+#endif
+                                 aom_svc_params_t *svc_params)
+{
+    AOMContext *ctx = avctx->priv_data;
+    char buf[80];
+    int res;
+
+    snprintf(buf, sizeof(buf), "%s:", ctlidstr[id]);
+
+    res = aom_codec_control(&ctx->encoder, id, svc_params);
+    if (res != AOM_CODEC_OK) {
+        snprintf(buf, sizeof(buf), "Failed to get %s codec control",
+                 ctlidstr[id]);
+        log_encoder_error(avctx, buf);
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
  static av_cold int aom_free(AVCodecContext *avctx)
  {
      AOMContext *ctx = avctx->priv_data;
@@ -673,6 +701,18 @@ static int choose_tiling(AVCodecContext *avctx,
      return 0;
  }
  +static void aom_svc_parse_int_array(int *dest, char *value, int 
max_entries)
+{
+    int dest_idx = 0;
+    char *saveptr = NULL;
+    char *token = av_strtok(value, ",", &saveptr);
+
+    while (token && dest_idx < max_entries) {
+        dest[dest_idx++] = strtoul(token, NULL, 10);
+        token = av_strtok(NULL, ",", &saveptr);
+    }
+}
+
  static av_cold int aom_init(AVCodecContext *avctx,
                              const struct aom_codec_iface *iface)
  {
@@ -968,6 +1008,40 @@ static av_cold int aom_init(AVCodecContext *avctx,
      if (ctx->enable_intrabc >= 0)
          codecctl_int(avctx, AV1E_SET_ENABLE_INTRABC, ctx->enable_intrabc);
  +    if (enccfg.rc_end_usage == AOM_CBR) {
+        aom_svc_params_t svc_params = {};
+        svc_params.framerate_factor[0] = 1;
+        svc_params.number_spatial_layers = 1;
+        svc_params.number_temporal_layers = 1;
+
+        const AVDictionaryEntry *en = NULL;
+        while ((en = av_dict_iterate(ctx->svc_parameters, en))) {
+            if (!strlen(en->value))
+                return AVERROR(EINVAL);
+
+            if (!strcmp(en->key, "number_spatial_layers"))
+                svc_params.number_spatial_layers = strtoul(en->value, 
NULL, 10);
+            else if (!strcmp(en->key, "number_temporal_layers"))
+                svc_params.number_temporal_layers = strtoul(en->value, 
NULL, 10);
+            else if (!strcmp(en->key, "max_quantizers"))
+                aom_svc_parse_int_array(svc_params.max_quantizers, 
en->value, AOM_MAX_LAYERS);
+            else if (!strcmp(en->key, "min_quantizers"))
+                aom_svc_parse_int_array(svc_params.min_quantizers, 
en->value, AOM_MAX_LAYERS);
+            else if (!strcmp(en->key, "scaling_factor_num"))
+                aom_svc_parse_int_array(svc_params.scaling_factor_num, 
en->value, AOM_MAX_SS_LAYERS);
+            else if (!strcmp(en->key, "scaling_factor_den"))
+                aom_svc_parse_int_array(svc_params.scaling_factor_den, 
en->value, AOM_MAX_SS_LAYERS);
+            else if (!strcmp(en->key, "layer_target_bitrate"))
+ 
aom_svc_parse_int_array(svc_params.layer_target_bitrate, en->value, 
AOM_MAX_LAYERS);
+            else if (!strcmp(en->key, "framerate_factor"))
+                aom_svc_parse_int_array(svc_params.framerate_factor, 
en->value, AOM_MAX_TS_LAYERS);
+        }
+
+        res = codecctl_svcp(avctx, AV1E_SET_SVC_PARAMS, &svc_params);
+        if (res < 0)
+            return res;
+    }
+
  #if AOM_ENCODER_ABI_VERSION >= 23
      {
          const AVDictionaryEntry *en = NULL;
@@ -1517,6 +1591,7 @@ static const AVOption options[] = {
      { "enable-masked-comp",           "Enable masked compound", 
                     OFFSET(enable_masked_comp), 
AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE},
      { "enable-interintra-comp",       "Enable interintra compound", 
                     OFFSET(enable_interintra_comp), 
AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE},
      { "enable-smooth-interintra",     "Enable smooth interintra mode", 
                     OFFSET(enable_smooth_interintra), 
AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE},
+    { "svc-parameters", "SVC configuration using a :-separated list of 
key=value parameters (only applied in CBR mode)", 
OFFSET(svc_parameters), AV_OPT_TYPE_DICT, { 0 }, 0, 0, VE},
  #if AOM_ENCODER_ABI_VERSION >= 23
      { "aom-params",                   "Set libaom options using a 
:-separated list of key=value pairs", OFFSET(aom_params), 
AV_OPT_TYPE_DICT, { 0 }, 0, 0, VE },
  #endif
-- 
2.34.1