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Quellcode

static AVStream *add_audio_stream(AVFormatContext *oc, enum CodecID codec_id)
{
    AVCodecContext *c;
    AVStream *st;
    
    st = av_new_stream(oc, 1);
    if (!st) {
        fprintf(stderr, "Could not alloc stream\n");
        exit(1);
    }
    
    c = st->codec;
    c->codec_id = codec_id;
    c->codec_type = CODEC_TYPE_AUDIO;
    
    c->sample_fmt = SAMPLE_FMT_S16;
    
    /* put sample parameters */
    c->bit_rate = 64000;
    c->sample_rate = 44100;
    c->channels = 2;
    return st;
}

static void open_audio(AVFormatContext *oc, AVStream *st)
{
    AVCodecContext *c;
    AVCodec *codec;
    
    c = st->codec;
    
    /* find the audio encoder */
    codec = avcodec_find_encoder(c->codec_id);
    if (!codec) {
        fprintf(stderr, "codec not found\n");
        exit(1);
    }
    
    /* open it */
    if (avcodec_open(c, codec) < 0) {
        fprintf(stderr, "could not open codec\n");
        exit(1);
    }
    
    /* init signal generator */
    t = 0;
    tincr = 2 * M_PI * 110.0 / c->sample_rate;
    /* increment frequency by 110 Hz per second */
    tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
    
    audio_outbuf_size = 10000;
    audio_outbuf = av_malloc(audio_outbuf_size);
    
    /* ugly hack for PCM codecs (will be removed ASAP with new PCM
     support to compute the input frame size in samples */
    if (c->frame_size <= 1) {
        audio_input_frame_size = audio_outbuf_size / c->channels;
        switch(st->codec->codec_id) {
            case CODEC_ID_PCM_S16LE:
            case CODEC_ID_PCM_S16BE:
            case CODEC_ID_PCM_U16LE:
            case CODEC_ID_PCM_U16BE:
                audio_input_frame_size >>= 1;
                break;
            default:
                break;
        }
    } else {
        audio_input_frame_size = c->frame_size;
    }
    
    samples = av_malloc(audio_input_frame_size * 2 * c->channels);
}

/* prepare a 16 bit dummy audio frame of 'frame_size' samples and
 'nb_channels' channels */
static void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
{
    int j, i, v;
    int16_t *q;
    
    q = samples;
    for(j=0;j<frame_size;j++) {
        v = (int)(sin(t) * 10000);
        for(i = 0; i < nb_channels; i++)
            *q++ = v;
        t += tincr;
        tincr += tincr2;
    }
}

static void write_audio_frame(AVFormatContext *oc, AVStream *st)
{
    AVCodecContext *c;
    AVPacket pkt;
    av_init_packet(&pkt);
    
    c = st->codec;
    
    get_audio_frame(samples, audio_input_frame_size, c->channels);
    
    pkt.size= avcodec_encode_audio(c, audio_outbuf, audio_outbuf_size, samples);
    
    if (c->coded_frame->pts != AV_NOPTS_VALUE)
        pkt.pts= av_rescale_q(c->coded_frame->pts, c->time_base, st->time_base);
    pkt.flags |= PKT_FLAG_KEY;
    pkt.stream_index= st->index;
    pkt.data= audio_outbuf;
    
    /* write the compressed frame in the media file */
    if (av_interleaved_write_frame(oc, &pkt) != 0) {
        fprintf(stderr, "Error while writing audio frame\n");
        exit(1);
    }
}

static void close_audio(AVFormatContext *oc, AVStream *st)
{
    avcodec_close(st->codec);
    
    av_free(samples);
    av_free(audio_outbuf);
}

Quellcode

AVStream *audioStream = add_audio_stream(pFormatCtxVideo, CODEC_ID_PCM_U16BE);
    
    open_audio(pFormatCtxVideo, audioStream);
    
    get_audio_frame(samples, audio_input_frame_size, 2);
    
    write_audio_frame(pFormatCtxVideo, audioStream);

Quellcode

0x00360ed0  <+0192>  ldr	r4, [r3, #48]