mpeg_audio.c

video linux conference

                    break;
                }

                /* Check info is in sync with previous one */
                if( i_next_channels_conf != p_sys->i_channels_conf ||
                    i_next_rate != p_sys->i_rate ||
                    i_next_layer != p_sys->i_layer ||
                    i_next_frame_length != p_sys->i_frame_length )
                {
                    /* Free bitrate only */
                    if( p_sys->i_bit_rate == 0 )
                    {
                        p_sys->i_frame_size++;
                        break;
                    }

                    msg_Dbg( p_dec, "parameters changed unexpectedly "
                             "(emulated startcode ?)" );
                    block_SkipByte( &p_sys->bytestream );
                    p_sys->i_state = STATE_NOSYNC;
                    break;
                }

                /* Free bitrate only */
                if( p_sys->i_bit_rate == 0 )
                {
                    if( i_next_bit_rate != 0 )
                    {
                        p_sys->i_frame_size++;
                        break;
                    }
                }

            }
            else
            {
                /* Free bitrate only */
                if( p_sys->i_bit_rate == 0 )
                {
                    if( (unsigned int)p_sys->i_frame_size >
                        p_sys->i_max_frame_size )
                    {
                        msg_Dbg( p_dec, "frame too big %d > %d "
                                 "(emulated startcode ?)", p_sys->i_frame_size,
                                 p_sys->i_max_frame_size );
                        block_SkipByte( &p_sys->bytestream );
                        p_sys->i_state = STATE_NOSYNC;
                        p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
                        break;
                    }

                    p_sys->i_frame_size++;
                    break;
                }

                msg_Dbg( p_dec, "emulated startcode "
                         "(no startcode on following frame)" );
                p_sys->i_state = STATE_NOSYNC;
                block_SkipByte( &p_sys->bytestream );
                break;
            }

            p_sys->i_state = STATE_SEND_DATA;
            break;

        case STATE_GET_DATA:
            /* Make sure we have enough data.
             * (Not useful if we went through NEXT_SYNC) */
            if( block_WaitBytes( &p_sys->bytestream,
                                 p_sys->i_frame_size ) != VLC_SUCCESS )
            {
                /* Need more data */
                return NULL;
            }
            p_sys->i_state = STATE_SEND_DATA;

        case STATE_SEND_DATA:
            if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
            {
                //p_dec->b_error = VLC_TRUE;
                return NULL;
            }

            /* Free bitrate only */
            if( p_sys->i_bit_rate == 0 )
            {
                p_sys->i_free_frame_size = p_sys->i_frame_size;
            }

            /* Copy the whole frame into the buffer. When we reach this point
             * we already know we have enough data available. */
            block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );

            /* Get beginning of next frame for libmad */
            if( !p_sys->b_packetizer )
            {
                memcpy( p_buf + p_sys->i_frame_size,
                        p_header, MAD_BUFFER_GUARD );
            }

            p_sys->i_state = STATE_NOSYNC;

            /* Make sure we don't reuse the same pts twice */
            if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
                p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;

            /* So p_block doesn't get re-added several times */
            *pp_block = block_BytestreamPop( &p_sys->bytestream );

            return p_out_buffer;
        }
    }

    return NULL;
}

/*****************************************************************************
 * GetOutBuffer:
 *****************************************************************************/
static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    uint8_t *p_buf;

    if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
    {
        msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
                  p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );

        aout_DateInit( &p_sys->end_date, p_sys->i_rate );
        aout_DateSet( &p_sys->end_date, p_sys->i_pts );
    }

    p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
    p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
    p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
    p_dec->fmt_out.audio.i_bytes_per_frame =
        p_sys->i_max_frame_size + MAD_BUFFER_GUARD;

    p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
    p_dec->fmt_out.audio.i_physical_channels =
        p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;

    p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;

    if( p_sys->b_packetizer )
    {
        block_t *p_sout_buffer = GetSoutBuffer( p_dec );
        p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
        *pp_out_buffer = p_sout_buffer;
    }
    else
    {
        aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
        p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
        *pp_out_buffer = p_aout_buffer;
    }

    return p_buf;
}

/*****************************************************************************
 * GetAoutBuffer:
 *****************************************************************************/
static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    aout_buffer_t *p_buf;

    p_buf = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_frame_length );
    if( p_buf == NULL ) return NULL;

    p_buf->start_date = aout_DateGet( &p_sys->end_date );
    p_buf->end_date =
        aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );

    /* Hack for libmad filter */
    p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;

    return p_buf;
}

/*****************************************************************************
 * GetSoutBuffer:
 *****************************************************************************/
static block_t *GetSoutBuffer( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    block_t *p_block;

    p_block = block_New( p_dec, p_sys->i_frame_size );
    if( p_block == NULL ) return NULL;

    p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );

    p_block->i_length =
        aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) -
            p_block->i_pts;

    return p_block;
}

/*****************************************************************************
 * CloseDecoder: clean up the decoder
 *****************************************************************************/
static void CloseDecoder( vlc_object_t *p_this )
{
    decoder_t *p_dec = (decoder_t *)p_this;
    decoder_sys_t *p_sys = p_dec->p_sys;

    block_BytestreamRelease( &p_sys->bytestream );

    free( p_sys );
}

/*****************************************************************************
 * SyncInfo: parse MPEG audio sync info
 *****************************************************************************/
static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
                     unsigned int * pi_channels_conf,
                     unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
                     unsigned int * pi_frame_length,
                     unsigned int * pi_max_frame_size, unsigned int * pi_layer)
{
    static const int ppi_bitrate[2][3][16] =
    {
        {
            /* v1 l1 */
            { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
              416, 448, 0},
            /* v1 l2 */
            { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
              320, 384, 0},
            /* v1 l3 */
            { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
              256, 320, 0}
        },

        {
            /* v2 l1 */
            { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
              224, 256, 0},
            /* v2 l2 */
            { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
              144, 160, 0},
            /* v2 l3 */
            { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
              144, 160, 0}
        }
    };

    static const int ppi_samplerate[2][4] = /* version 1 then 2 */
    {
        { 44100, 48000, 32000, 0 },
        { 22050, 24000, 16000, 0 }
    };

    int i_version, i_mode, i_emphasis;
    vlc_bool_t b_padding, b_mpeg_2_5, b_crc;
    int i_frame_size = 0;
    int i_bitrate_index, i_samplerate_index;
    int i_max_bit_rate;

    b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
    i_version   = 1 - ((i_header & 0x80000) >> 19);
    *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
    b_crc = !((i_header >> 16) & 0x01);
    i_bitrate_index = (i_header & 0xf000) >> 12;
    i_samplerate_index = (i_header & 0xc00) >> 10;
    b_padding   = (i_header & 0x200) >> 9;
    /* Extension */
    i_mode      = (i_header & 0xc0) >> 6;
    /* Modeext, copyright & original */
    i_emphasis  = i_header & 0x3;

    if( *pi_layer != 4 &&
        i_bitrate_index < 0x0f &&
        i_samplerate_index != 0x03 &&
        i_emphasis != 0x02 )
    {
        switch ( i_mode )
        {
        case 0: /* stereo */
        case 1: /* joint stereo */
            *pi_channels = 2;
            *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
            break;
        case 2: /* dual-mono */
            *pi_channels = 2;
            *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
                                | AOUT_CHAN_DUALMONO;
            break;
        case 3: /* mono */
            *pi_channels = 1;
            *pi_channels_conf = AOUT_CHAN_CENTER;
            break;
        }
        *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
        i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
        *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];

        if ( b_mpeg_2_5 )
        {
            *pi_sample_rate >>= 1;
        }

        switch( *pi_layer )
        {
        case 1:
            i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
                           b_padding ) * 4;
            *pi_max_frame_size = ( 12000 * i_max_bit_rate /
                                 *pi_sample_rate + 1 ) * 4;
            *pi_frame_length = 384;
            break;

        case 2:
            i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
            *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
            *pi_frame_length = 1152;
            break;

        case 3:
            i_frame_size = ( i_version ? 72000 : 144000 ) *
                           *pi_bit_rate / *pi_sample_rate + b_padding;
            *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
                                 i_max_bit_rate / *pi_sample_rate + 1;
            *pi_frame_length = i_version ? 576 : 1152;
            break;

        default:
            break;
        }
    }
    else
    {
        return -1;
    }

    return i_frame_size;
}