a52.c

video linux conference

/*****************************************************************************
 * a52.c: parse A/52 audio sync info and packetize the stream
 *****************************************************************************
 * Copyright (C) 2001-2002 VideoLAN
 * $Id: a52.c 10101 2005-03-02 16:47:31Z robux4 $
 *
 * Authors: St閜hane Borel <[e-mail]>
 *          Christophe Massiot <[e-mail]>
 *          Gildas Bazin <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#include <vlc/vlc.h>
#include <vlc/decoder.h>

#include "vlc_block_helper.h"

#define A52_HEADER_SIZE 7

/*****************************************************************************
 * decoder_sys_t : decoder descriptor
 *****************************************************************************/
struct decoder_sys_t
{
    /* Module mode */
    vlc_bool_t b_packetizer;

    /*
     * Input properties
     */
    int i_state;

    block_bytestream_t bytestream;

    /*
     * Common properties
     */
    audio_date_t   end_date;

    mtime_t i_pts;
    int i_frame_size, i_bit_rate;
    unsigned int i_rate, i_channels, i_channels_conf;

};

enum {

    STATE_NOSYNC,
    STATE_SYNC,
    STATE_HEADER,
    STATE_NEXT_SYNC,
    STATE_GET_DATA,
    STATE_SEND_DATA
};

/****************************************************************************
 * Local prototypes
 ****************************************************************************/
static int  OpenDecoder   ( vlc_object_t * );
static int  OpenPacketizer( vlc_object_t * );
static void CloseDecoder  ( vlc_object_t * );
static void *DecodeBlock  ( decoder_t *, block_t ** );

static int  SyncInfo      ( const byte_t *, int *, int *, int *,int * );

static uint8_t       *GetOutBuffer ( decoder_t *, void ** );
static aout_buffer_t *GetAoutBuffer( decoder_t * );
static block_t       *GetSoutBuffer( decoder_t * );

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
vlc_module_begin();
    set_description( _("A/52 parser") );
    set_capability( "decoder", 100 );
    set_callbacks( OpenDecoder, CloseDecoder );
    set_category( CAT_INPUT );
    set_subcategory( SUBCAT_INPUT_ACODEC );

    add_submodule();
    set_description( _("A/52 audio packetizer") );
    set_capability( "packetizer", 10 );
    set_callbacks( OpenPacketizer, CloseDecoder );
vlc_module_end();

/*****************************************************************************
 * OpenDecoder: probe the decoder and return score
 *****************************************************************************/
static int OpenDecoder( vlc_object_t *p_this )
{
    decoder_t *p_dec = (decoder_t*)p_this;
    decoder_sys_t *p_sys;

    if( p_dec->fmt_in.i_codec != VLC_FOURCC('a','5','2',' ')
          && p_dec->fmt_in.i_codec != VLC_FOURCC('a','5','2','b') )
    {
        return VLC_EGENERIC;
    }

    /* Allocate the memory needed to store the decoder's structure */
    if( ( p_dec->p_sys = p_sys =
          (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
    {
        msg_Err( p_dec, "out of memory" );
        return VLC_EGENERIC;
    }

    /* Misc init */
    p_sys->b_packetizer = VLC_FALSE;
    p_sys->i_state = STATE_NOSYNC;
    aout_DateSet( &p_sys->end_date, 0 );

    p_sys->bytestream = block_BytestreamInit( p_dec );

    /* Set output properties */
    p_dec->fmt_out.i_cat = AUDIO_ES;
    p_dec->fmt_out.i_codec = VLC_FOURCC('a','5','2',' ');
    p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */

    /* Set callback */
    p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
        DecodeBlock;
    p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
        DecodeBlock;

    return VLC_SUCCESS;
}

static int OpenPacketizer( vlc_object_t *p_this )
{
    decoder_t *p_dec = (decoder_t*)p_this;

    int i_ret = OpenDecoder( p_this );

    if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = VLC_TRUE;

    return i_ret;
}

/****************************************************************************
 * DecodeBlock: the whole thing
 ****************************************************************************
 * This function is called just after the thread is launched.
 ****************************************************************************/
static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    uint8_t p_header[A52_HEADER_SIZE];
    uint8_t *p_buf;
    void *p_out_buffer;

    if( !pp_block || !*pp_block ) return NULL;

    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|BLOCK_FLAG_CORRUPTED) )
    {
        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 )
            {
                if( p_header[0] == 0x0b && p_header[1] == 0x77 )
                {
                    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;

        case STATE_HEADER:
            /* Get A/52 frame header (A52_HEADER_SIZE bytes) */
            if( block_PeekBytes( &p_sys->bytestream, p_header,
                                 A52_HEADER_SIZE ) != VLC_SUCCESS )
            {
                /* Need more data */
                return NULL;
            }

            /* Check if frame is valid and get frame info */
            p_sys->i_frame_size = SyncInfo( p_header,
                                            &p_sys->i_channels,
                                            &p_sys->i_channels_conf,
                                            &p_sys->i_rate,
                                            &p_sys->i_bit_rate );
            if( !p_sys->i_frame_size )
            {
                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 pp_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_header, 2 )
                != VLC_SUCCESS )
            {
                /* Need more data */
                return NULL;
            }

            if( p_sys->b_packetizer &&
                p_header[0] == 0 && p_header[1] == 0 )
            {
                /* A52 wav files and audio CD's use stuffing */
                p_sys->i_state = STATE_GET_DATA;
                break;
            }