for(pos=0; pos < s->pb.buffer_size-1; pos++) if( s->pb.buffer[pos] == 0xFF && (s->pb.buffer[pos] & 0xE0) == 0xE0 ) break;  if( pos < s->pb.buffer_size-1 && (s->pb.buffer[pos+1] & 6) == 2 ) st->codec.codec_id = CODEC_ID_MP3LAME;
static int mp3_read_header(AVFormatContext *s,                           AVFormatParameters *ap){    AVStream *st;    st = av_new_stream(s, 0);    if (!st)        return AVERROR_NOMEM;    st->codec.codec_type = CODEC_TYPE_AUDIO;    st->codec.codec_id = CODEC_ID_MP2;    /* the parameters will be extracted from the compressed bitstream */    return 0;}