[Libav-user] avcodec_encode_audio() usage

Marlon Reid Marlon at scansoft.co.za
Wed Oct 12 08:05:44 CEST 2011


I have a small application that takes a raw pcm stream, encodes it to
mp3 and streams it to something like VLC. I am however havinging issues
with encoding my raw pcm stream. The problem is that my outbuf from
avcodec_encode_audio() is always  uninitialized.  It is as if
avcodec_encode_audio() never modifies outbuf.
In any case, here is my function


unsigned char* CEncoder::encode_audio_frame(unsigned char*
in_pcm_buffer, int in_pcm_buffer_size, unsigned char * mp3_buffer, int
*out_size, std::string encoding)

AVCodec *codec;
AVCodecContext *c= NULL;
int outbuf_size;
uint8_t *outbuf;


codec = avcodec_find_encoder(CODEC_ID_MP3);
c = avcodec_alloc_context3(codec);

/* put sample parameters */
c->bit_rate = 64000;
c->sample_rate = SAMPLE_RATE;
c->channels = NUM_CHANNELS;
c->sample_fmt = AV_SAMPLE_FMT_S16;

avcodec_open(c, codec)
frame_size = c->frame_size;
 uint8_t * outbuf = new uint8_t [ outbuf_size ] ;

/* encode the samples */
*out_size = avcodec_encode_audio(c, outbuf, outbuf_size,

return outbuf;
I suspect that I am using the avcodec_encode_audio() incorrectly.  Any
assistance will be great.
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