mpeg4audio.c

video linux conference

    if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
    {
        /* We've just started the stream, wait for the first PTS. */
        block_Release( *pp_block );
        return NULL;
    }

    if( (*pp_block)->i_flags&BLOCK_FLAG_DISCONTINUITY )
    {
        p_sys->i_state = STATE_NOSYNC;
    }

    block_BytestreamPush( &p_sys->bytestream, *pp_block );

    while( 1 )
    {
        switch( p_sys->i_state )
        {

        case STATE_NOSYNC:
            while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
                   == VLC_SUCCESS )
            {
                /* Look for sync word - should be 0xfff + 2 layer bits */
                if( p_header[0] == 0xff && (p_header[1] & 0xf6) == 0xf0 )
                {
                    p_sys->i_state = STATE_SYNC;
                    break;
                }
                block_SkipByte( &p_sys->bytestream );
            }
            if( p_sys->i_state != STATE_SYNC )
            {
                block_BytestreamFlush( &p_sys->bytestream );

                /* Need more data */
                return NULL;
            }

        case STATE_SYNC:
            /* New frame, set the Presentation Time Stamp */
            p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
            if( p_sys->i_pts != 0 &&
                p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
            {
                aout_DateSet( &p_sys->end_date, p_sys->i_pts );
            }
            p_sys->i_state = STATE_HEADER;
            break;

        case STATE_HEADER:
            /* Get ADTS frame header (ADTS_HEADER_SIZE bytes) */
            if( block_PeekBytes( &p_sys->bytestream, p_header,
                                 ADTS_HEADER_SIZE ) != VLC_SUCCESS )
            {
                /* Need more data */
                return NULL;
            }

            /* Check if frame is valid and get frame info */
            p_sys->i_frame_size = ADTSSyncInfo( p_dec, p_header,
                                                &p_sys->i_channels,
                                                &p_sys->i_rate,
                                                &p_sys->i_frame_length,
                                                &p_sys->i_header_size,
                                                &p_sys->i_raw_blocks );
            if( p_sys->i_frame_size <= 0 )
            {
                msg_Dbg( p_dec, "emulated sync word" );
                block_SkipByte( &p_sys->bytestream );
                p_sys->i_state = STATE_NOSYNC;
                break;
            }

            p_sys->i_state = STATE_NEXT_SYNC;

        case STATE_NEXT_SYNC:
            /* TODO: If p_block == NULL, flush the buffer without checking the
             * next sync word */

            /* Check if next expected frame contains the sync word */
            if( block_PeekOffsetBytes( &p_sys->bytestream, p_sys->i_frame_size
                                       + p_sys->i_header_size, p_header, 2 )
                != VLC_SUCCESS )
            {
                /* Need more data */
                return NULL;
            }

            if( p_header[0] != 0xff || (p_header[1] & 0xf6) != 0xf0 )
            {
                msg_Dbg( p_dec, "emulated sync word "
                         "(no sync 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 +
                                 p_sys->i_header_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;
            }

            /* When we reach this point we already know we have enough
             * data available. */

            /* Skip the ADTS header */
            block_SkipBytes( &p_sys->bytestream, p_sys->i_header_size );

            /* Copy the whole frame into the buffer */
            block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );

            /* 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 );

            p_sys->i_state = STATE_NOSYNC;

            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;
    block_t *p_block;

    if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
    {
        msg_Info( p_dec, "AAC channels: %d samplerate: %d",
                  p_sys->i_channels, p_sys->i_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_bytes_per_frame = p_sys->i_frame_size;
    p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;

#if 0
    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;
#endif

    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;

    *pp_out_buffer = p_block;
    return p_block->p_buffer;
}

/*****************************************************************************
 * ClosePacketizer: clean up the packetizer
 *****************************************************************************/
static void ClosePacketizer( 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_dec->p_sys );
}

/*****************************************************************************
 * ADTSSyncInfo: parse MPEG 4 audio ADTS sync info
 *****************************************************************************/
static int ADTSSyncInfo( decoder_t * p_dec, const byte_t * p_buf,
                         unsigned int * pi_channels,
                         unsigned int * pi_sample_rate,
                         unsigned int * pi_frame_length,
                         unsigned int * pi_header_size,
                         unsigned int * pi_raw_blocks_in_frame )
{
    int i_id, i_profile, i_sample_rate_idx, i_frame_size;
    vlc_bool_t b_crc;

    /* Fixed header between frames */
    i_id = ( (p_buf[1] >> 3) & 0x01 ) ? 2 : 4;
    b_crc = !(p_buf[1] & 0x01);
    i_profile = p_buf[2] >> 6;
    i_sample_rate_idx = (p_buf[2] >> 2) & 0x0f;
    *pi_sample_rate = i_sample_rates[i_sample_rate_idx];
    *pi_channels = ((p_buf[2] & 0x01) << 2) | ((p_buf[3] >> 6) & 0x03);

    /* Variable header */
    i_frame_size = ((p_buf[3] & 0x03) << 11) | (p_buf[4] << 3) |
                   ((p_buf[5] >> 5) & 0x7);
    *pi_raw_blocks_in_frame = (p_buf[6] & 0x02) + 1;

    if( !*pi_sample_rate || !*pi_channels || !i_frame_size )
    {
        return 0;
    }

    /* Fixme */
    *pi_frame_length = 1024;

    /* Build the decoder specific info header */
    if( !p_dec->fmt_out.i_extra )
    {
        p_dec->fmt_out.i_extra = 2;
        p_dec->fmt_out.p_extra = malloc( 2 );
        ((uint8_t *)p_dec->fmt_out.p_extra)[0] =
            (i_profile + 1) << 3 | (i_sample_rate_idx >> 1);
        ((uint8_t *)p_dec->fmt_out.p_extra)[1] =
            ((i_sample_rate_idx & 0x01) << 7) | (*pi_channels <<3);
    }

    /* ADTS header length */
    *pi_header_size = b_crc ? 9 : 7;

    return i_frame_size - *pi_header_size;
}