voc.c

uclinux 下的vlc播放器源代码

                else
                    p_sys->i_loop_count--;
            }
            break;

        case 8: 
            /* 
             * Block 8 is a big kludge to add stereo support to block 1 :
             * A block of type 8 is always followed by a block of type 1
             * and specifies the number of channels in that 1-block
             * (normally block 1 are always mono). In practice, block type 9
             * is used for stereo rather than 8
             */
            if( ( i_block_size != 4 )
             || ( stream_Read( p_demux->s, buf, 4 ) < 4 ) )
                goto corrupt;

            if( buf[2] )
            {
                msg_Err( p_demux, "unsupported compression" );
                return VLC_EGENERIC;
            }

            new_fmt.i_codec = VLC_FOURCC('u','8',' ',' ');
            new_fmt.audio.i_channels = buf[3] + 1; /* can't be nul */
            new_fmt.audio.i_rate = 256000000L /
                          ((65536L - GetWLE(buf)) * new_fmt.audio.i_channels);
            new_fmt.audio.i_bytes_per_frame = new_fmt.audio.i_channels;
            new_fmt.audio.i_frame_length = 1;
            new_fmt.audio.i_blockalign = new_fmt.audio.i_bytes_per_frame;
            new_fmt.audio.i_bitspersample = 8 * new_fmt.audio.i_bytes_per_frame;
            new_fmt.i_bitrate = new_fmt.audio.i_rate * 8;

            /* read subsequent block 1 */
            if( stream_Read( p_demux->s, buf, 4 ) < 4 )
                return VLC_EGENERIC; /* EOF */
        
            i_block_size = GetDWLE( buf ) >> 8;
            msg_Dbg( p_demux, "new block: type: %u, size: %u",
                    (unsigned)*buf, i_block_size );
            if( i_block_size < 2 )
                goto corrupt;
            i_block_size -= 2;

            if( stream_Read( p_demux->s, buf, 2 ) < 2 )
                goto corrupt;

            if( buf[1] )
            {
                msg_Err( p_demux, "unsupported compression" );
                return VLC_EGENERIC;
            }

            break;

        case 9: /* newer data block with channel number and bits resolution */
            if( i_block_size < 12 )
                goto corrupt;
            i_block_size -= 12;

            if( ( stream_Read( p_demux->s, buf, 8 ) < 8 )
             || ( stream_Read( p_demux->s, NULL, 4 ) < 4 ) )
                goto corrupt;

            new_fmt.audio.i_rate = GetDWLE( buf );
            new_fmt.audio.i_bitspersample = buf[4];
            new_fmt.audio.i_channels = buf[5];

            switch( GetWLE( &buf[6] ) ) /* format */
            {
                case 0x0000: /* PCM */
                    switch( new_fmt.audio.i_bitspersample )
                    {
                        case 8:
                            new_fmt.i_codec = VLC_FOURCC('u','8',' ',' ');
                            break;

                        case 16:
                            new_fmt.i_codec = VLC_FOURCC('u','1','6','l');
                            break;

                        default:
                            msg_Err( p_demux, "unsupported bit res.: %u bits",
                                     new_fmt.audio.i_bitspersample );
                            return VLC_EGENERIC;
                    }
                    break;

                case 0x0004: /* signed */
                    switch( new_fmt.audio.i_bitspersample )
                    {
                        case 8:
                            new_fmt.i_codec = VLC_FOURCC('s','8',' ',' ');
                            break;

                        case 16:
                            new_fmt.i_codec = VLC_FOURCC('s','1','6','l');
                            break;

                        default:
                            msg_Err( p_demux, "unsupported bit res.: %u bits",
                                     new_fmt.audio.i_bitspersample );
                            return VLC_EGENERIC;
                    }
                    break;

                default: 
                    msg_Err( p_demux, "unsupported compression" );
                    return VLC_EGENERIC;
            }

            new_fmt.audio.i_bytes_per_frame = new_fmt.audio.i_channels
                * (new_fmt.audio.i_bitspersample / 8);
            new_fmt.audio.i_frame_length = 1;
            new_fmt.audio.i_blockalign = new_fmt.audio.i_bytes_per_frame;
            new_fmt.i_bitrate = 8 * new_fmt.audio.i_rate
                                     * new_fmt.audio.i_bytes_per_frame;
            break;

        default:
            msg_Dbg( p_demux, "unknown block type %u - skipping block",
                     (unsigned)*buf);
        case 4: /* blocks of non-audio types can be skipped */
        case 5:
            if( stream_Read( p_demux->s, NULL, i_block_size ) < i_block_size )
                goto corrupt;
            i_block_size = 0;
            break;
    }

    p_sys->i_block_start = stream_Tell( p_demux->s );
    p_sys->i_block_end = p_sys->i_block_start + i_block_size;

    if( i_block_size || p_sys->i_silence_countdown )
    {
        /* we've read a block with data in it - update decoder */
        msg_Dbg( p_demux, "fourcc: %4.4s, channels: %d, "
                 "freq: %d Hz, bitrate: %dKo/s, blockalign: %d, "
                 "bits/samples: %d", (char *)&new_fmt.i_codec,
                 new_fmt.audio.i_channels, new_fmt.audio.i_rate,
                 new_fmt.i_bitrate / 8192, new_fmt.audio.i_blockalign,
                 new_fmt.audio.i_bitspersample );

        if( ( p_sys->p_es != NULL ) && fmtcmp( &p_sys->fmt, &new_fmt ) )
        {
            msg_Dbg( p_demux, "codec change needed" );
            es_out_Del( p_demux->out, p_sys->p_es );
            p_sys->p_es = NULL;
        }

        if( p_sys->p_es == NULL )
        {
            memcpy( &p_sys->fmt, &new_fmt, sizeof( p_sys->fmt ) );
            date_Change( &p_sys->pts, p_sys->fmt.audio.i_rate, 1 );
            p_sys->p_es = es_out_Add( p_demux->out, &p_sys->fmt );
        }
    }

    return VLC_SUCCESS;

corrupt:
    msg_Err( p_demux, "corrupted file - halting demux" );
    return VLC_EGENERIC;
}

/*****************************************************************************
 * Demux: read packet and send them to decoders
 *****************************************************************************
 * Returns -1 in case of error, 0 in case of EOF, 1 otherwise
 *****************************************************************************/
#define SAMPLES_BUFFER 1000
static int Demux( demux_t *p_demux )
{
    demux_sys_t *p_sys = p_demux->p_sys;
    block_t     *p_block;
    int64_t     i_offset, i;

    i_offset = stream_Tell( p_demux->s );

    while( ( i_offset >= p_sys->i_block_end )
         && ( p_sys->i_silence_countdown == 0 ) )
        if( ReadBlockHeader( p_demux ) != VLC_SUCCESS )
            return 0;

    if( p_sys->i_silence_countdown == 0 )
    {
        i = ( p_sys->i_block_end - i_offset )
            / p_sys->fmt.audio.i_bytes_per_frame;
        if( i > SAMPLES_BUFFER )
            i = SAMPLES_BUFFER;

        p_block = stream_Block( p_demux->s,
                                p_sys->fmt.audio.i_bytes_per_frame * i );
        if( p_block == NULL )
        {
            msg_Warn( p_demux, "cannot read data" );
            return 0;
        }
    }
    else
    {   /* emulates silence from the stream */
        i = p_sys->i_silence_countdown;
        if( i > SAMPLES_BUFFER )
            i = SAMPLES_BUFFER;

        p_block = block_New( p_demux, i );
        if( p_block == NULL )
            return VLC_ENOMEM;

        memset( p_block->p_buffer, 0, i );
        p_sys->i_silence_countdown -= i;
    }

    p_block->i_dts = p_block->i_pts =
        date_Increment( &p_sys->pts, p_sys->fmt.audio.i_frame_length * i );

    es_out_Control( p_demux->out, ES_OUT_SET_PCR, p_block->i_pts );

    es_out_Send( p_demux->out, p_sys->p_es, p_block );

    return 1;
}

/*****************************************************************************
 * Close: frees unused data
 *****************************************************************************/
static void Close ( vlc_object_t * p_this )
{
    demux_sys_t *p_sys  = ((demux_t *)p_this)->p_sys;

    free( p_sys );
}

/*****************************************************************************
 * Control:
 *****************************************************************************/
static int Control( demux_t *p_demux, int i_query, va_list args )
{
    demux_sys_t *p_sys  = p_demux->p_sys;

    return demux2_vaControlHelper( p_demux->s, p_sys->i_block_start,
                                   p_sys->i_block_end,
                                   p_sys->fmt.i_bitrate,
                                   p_sys->fmt.audio.i_blockalign,
                                   i_query, args );
}