memset(c, 0, sizeof(*c));
c= avcodec_alloc_context();
void audio_encode_example(const char *filename){    AVCodec *codec;    AVCodecContext codec_context, *c = &codec_context;    int frame_size, i, j, out_size, outbuf_size;    FILE *f;    short *samples;    float t, tincr;    UINT8 *outbuf;    printf("Audio encoding\n");    /* find the MP2 encoder */    codec = avcodec_find_encoder(CODEC_ID_MP2);    if (!codec) {        fprintf(stderr, "codec not found\n");        exit(1);    }    /* put default values */    memset(c, 0, sizeof(*c));    /* put sample parameters */    c->bit_rate = 64000;    c->sample_rate = 44100;    c->channels = 2;    /* 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;    samples = malloc(frame_size * 2 * c->channels);    outbuf_size = 10000;    outbuf = malloc(outbuf_size);    f = fopen(filename, "w");    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);}