Fix compatibility with FFmpeg5.0 (#581)

Signed-off-by: bchoi <[email protected]>

Author: bchoineubility

av/src/AudioDecoder.cc

@@ -157,7 +157,11 @@ bool AudioDecoder::Decode(uint8_t **_outBuffer, unsigned int *_outBufferSize)
         // decodedFrame->linesize[0].
         int size = decodedFrame->nb_samples *
           av_get_bytes_per_sample(this->data->codecCtx->sample_fmt) *
+#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(59, 24, 100)
           this->data->codecCtx->ch_layout.nb_channels;
+#else
+          this->data->codecCtx->channels;
+#endif
         // Resize the audio buffer as necessary
         if (*_outBufferSize + size > maxBufferSize)
         {