Write silence audio data into file ffmpeg C++

Question

I want to write silence/zeroed audio sampled data into mov media container file inside audio data. My audio data is G711 linear PCM-mulaw encoded data with one channel. Currently my code looks like:

AVFrame* pSilentData = av_frame_alloc();
memset(&pSilentData->data[0], 0, iDataSize);
pkt.data = (uint8_t*) pSilentData;
pkt.size = iDataSize;

// ...

av_freep(&pSilentData->data[0]);
av_frame_free(&pSilentData);

But this sounds noise like dot dot instead of silence. What's the problem?

Answer 1

For µ-law audio the zero value is represented as 0xff, so change:

memset(&pSilentData->data[0], 0, iDataSize);

to:

memset(&pSilentData->data[0], 0xff, iDataSize);