Merge pull request #136 from yilun-zhangs/IAMF-OPUS

fix iamf-opus non-48kHz issue

Author: yilun-zhangs

code/src/iamf_dec/IAMF_decoder.c

@@ -626,8 +626,9 @@ static int iamf_codec_conf_get_sampling_rate(IAMF_CodecConf *c) {
     if (c->decoder_conf_size < 6) return IAMF_ERR_BAD_ARG;
     return reads32be(c->decoder_conf, 2);
   } else if (cid == IAMF_CODEC_OPUS) {
-    if (c->decoder_conf_size < 8) return IAMF_ERR_BAD_ARG;
-    return reads32be(c->decoder_conf, 4);
+    // https://aomediacodec.github.io/iamf/v1.1.0.html#opus-specific
+    // The sample rate used for computing offsets SHALL be 48 kHz.
+    return 48000;
   } else if (cid == IAMF_CODEC_AAC) {
     BitStream b;
     int ret, type;

code/src/iamf_dec/opus/IAMF_opus_decoder.c

@@ -80,7 +80,7 @@ static int iamf_opus_init(IAMF_CodecContext *ths) {
     return IAMF_ERR_BAD_ARG;
   }
 
-  ths->sample_rate = readu32be(config, 4);
+  ths->sample_rate = 48000;  // readu32be(config, 4);
   ths->channel_mapping_family = config[10];
 
   ctx->dec = opus_multistream2_decoder_create(ths->sample_rate, ths->streams,