Encoding Speex with libavcodec (FFMpeg)? - encoding

Question

I successfully compiled libavcodec with speex enabled.
I modified example from FFMPEG docs to encode the sample audio into Speex.
But the result file cannot be played with VLC Player(which has Speex decoder).
Any tips?
static void audio_encode_example(const char *filename)
{
AVCodec *codec;
AVCodecContext *c= NULL;
int frame_size, i, j, out_size, outbuf_size;
FILE *f;
short *samples;
float t, tincr;
uint8_t *outbuf;
printf("Audio encoding\n");
/* find the MP2 encoder */
codec = avcodec_find_encoder(CODEC_ID_SPEEX);
if (!codec) {
fprintf(stderr, "codec not found\n");
exit(1);
}
c= avcodec_alloc_context();
/* put sample parameters */
c->bit_rate = 64000;
c->sample_rate = 32000;
c->channels = 2;
c->sample_fmt=AV_SAMPLE_FMT_S16;
/* open it */
if (avcodec_open(c, codec) < 0) {
fprintf(stderr, "could not open codec\n");
exit(1);
}
/* the codec gives us the frame size, in samples */
frame_size = c->frame_size;
printf("frame size %d\n",frame_size);
samples =(short*) malloc(frame_size * 2 * c->channels);
outbuf_size = 10000;
outbuf =( uint8_t*) malloc(outbuf_size);
f = fopen(filename, "wb");
if (!f) {
fprintf(stderr, "could not open %s\n", filename);
exit(1);
}
/* encode a single tone sound */
t = 0;
tincr = 2 * M_PI * 440.0 / c->sample_rate;
for(i=0;i<200;i++) {
for(j=0;j<frame_size;j++) {
samples[2*j] = (int)(sin(t) * 10000);
samples[2*j+1] = samples[2*j];
t += tincr;
}
/* encode the samples */
out_size = avcodec_encode_audio(c, outbuf, outbuf_size, samples);
fwrite(outbuf, 1, out_size, f);
}
fclose(f);
free(outbuf);
free(samples);
avcodec_close(c);
av_free(c);
}
int main(int argc, char **argv)
{
avcodec_register_all();
audio_encode_example(argv[1]);
return 0;
}

Answer 1

Does Speex (I don't know it) by chance require a container format into which these frames are placed, with some kind of header? You're just taking the output of an encoder and dumping into a file without going through any formatting (libavformat).
Try encoding the same data into Speex using the ffmpeg command line utility and see if the resulting file plays.
I'm looking at some info at www.speex.org and it seems that speex data is put into .ogg files. The player you are using might not recognize raw Speex data, but only if it is wrapped in .ogg.
Though not a 100% definite answer, I hope this is of some help!