[FFmpeg-devel] [PATCH] avformat/iamf_writer: fix setting num_samples_per_frame for OPUS

[James Almer]

As per section 3.11.1 of the IAMF spec, the sample rate used in Codec Config
for Opus shall be 48kHz, regardless of the original sample rate used during
encoding.

Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavformat/iamf_writer.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/libavformat/iamf_writer.c b/libavformat/iamf_writer.c
index f15dabcb3e..467f839baf 100644
--- a/libavformat/iamf_writer.c
+++ b/libavformat/iamf_writer.c
@@ -112,9 +112,17 @@ static int fill_codec_config(IAMFContext *iamf, const AVStreamGroup *stg,
     int j, ret = 0;
 
     codec_config->codec_id = st->codecpar->codec_id;
-    codec_config->sample_rate = st->codecpar->sample_rate;
     codec_config->codec_tag = st->codecpar->codec_tag;
-    codec_config->nb_samples = st->codecpar->frame_size;
+    switch (codec_config->codec_id) {
+    case AV_CODEC_ID_OPUS:
+        codec_config->sample_rate = 48000;
+        codec_config->nb_samples = av_rescale(st->codecpar->frame_size, 48000, st->codecpar->sample_rate);
+        break;
+    default:
+        codec_config->sample_rate = st->codecpar->sample_rate;
+        codec_config->nb_samples = st->codecpar->frame_size;
+        break;
+    }
     populate_audio_roll_distance(codec_config);
     if (st->codecpar->extradata_size) {
         codec_config->extradata = av_memdup(st->codecpar->extradata, st->codecpar->extradata_size);
@@ -183,9 +191,9 @@ static int add_param_definition(IAMFContext *iamf, AVIAMFParamDefinition *param,
     }
     if (codec_config) {
         if (!param->duration)
-            param->duration = codec_config->nb_samples;
+            param->duration = av_rescale(codec_config->nb_samples, param->parameter_rate, codec_config->sample_rate);
         if (!param->constant_subblock_duration)
-            param->constant_subblock_duration = codec_config->nb_samples;
+            param->constant_subblock_duration = av_rescale(codec_config->nb_samples, param->parameter_rate, codec_config->sample_rate);
     }
 
     param_definition = av_mallocz(sizeof(*param_definition));
-- 
2.47.1