mpegvideo.c

video linux conference

/*****************************************************************************
 * mpegvideo.c: parse and packetize an MPEG1/2 video stream
 *****************************************************************************
 * Copyright (C) 2001, 2002 VideoLAN
 * $Id: mpegvideo.c 10101 2005-03-02 16:47:31Z robux4 $
 *
 * Authors: Laurent Aimar <[e-mail]>
 *          Eric Petit <[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.
 *****************************************************************************/

/*****************************************************************************
 * Problem with this implementation:
 *
 * Although we should time-stamp each picture with a PTS, this isn't possible
 * with the current implementation.
 * The problem comes from the fact that for non-low-delay streams we can't
 * calculate the PTS of pictures used as backward reference. Even the temporal
 * reference number doesn't help here because all the pictures don't
 * necessarily have the same duration (eg. 3:2 pulldown).
 *
 * However this doesn't really matter as far as the MPEG muxers are concerned
 * because they allow having empty PTS fields. --gibalou
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#include <stdlib.h>                                      /* malloc(), free() */

#include <vlc/vlc.h>
#include <vlc/decoder.h>
#include <vlc/input.h>

#include "vlc_block_helper.h"

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
static int  Open ( vlc_object_t * );
static void Close( vlc_object_t * );

vlc_module_begin();
    set_category( CAT_SOUT );
    set_subcategory( SUBCAT_SOUT_PACKETIZER );
    set_description( _("MPEG-I/II video packetizer") );
    set_capability( "packetizer", 50 );
    set_callbacks( Open, Close );
vlc_module_end();

/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static block_t *Packetize( decoder_t *, block_t ** );
static block_t *ParseMPEGBlock( decoder_t *, block_t * );

struct decoder_sys_t
{
    /*
     * Input properties
     */
    block_bytestream_t bytestream;
    int i_state;
    int i_offset;
    uint8_t p_startcode[3];

    /* Sequence header and extension */
    block_t *p_seq;
    block_t *p_ext;

    /* Current frame being built */
    block_t    *p_frame;
    block_t    **pp_last;

    vlc_bool_t b_frame_slice;
    mtime_t i_pts;
    mtime_t i_dts;

    /* Sequence properties */
    int         i_frame_rate;
    int         i_frame_rate_base;
    vlc_bool_t  b_seq_progressive;
    vlc_bool_t  b_low_delay;
    int         i_aspect_ratio_info;
    vlc_bool_t  b_inited;

    /* Picture properties */
    int i_temporal_ref;
    int i_picture_type;
    int i_picture_structure;
    int i_top_field_first;
    int i_repeat_first_field;
    int i_progressive_frame;

    mtime_t i_interpolated_dts;
    mtime_t i_old_duration;
    mtime_t i_last_ref_pts;

    /* Number of pictures since last sequence header */
    int i_seq_old;

};

enum {
    STATE_NOSYNC,
    STATE_NEXT_SYNC
};

/*****************************************************************************
 * Open:
 *****************************************************************************/
static int Open( 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( 'm', 'p', 'g', '1' ) &&
        p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
        p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
    {
        return VLC_EGENERIC;
    }

    es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
    p_dec->pf_packetize = Packetize;

    p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );

    /* Misc init */
    p_sys->i_state = STATE_NOSYNC;
    p_sys->bytestream = block_BytestreamInit( p_dec );
    p_sys->p_startcode[0] = 0;
    p_sys->p_startcode[1] = 0;
    p_sys->p_startcode[2] = 1;
    p_sys->i_offset = 0;

    p_sys->p_seq = NULL;
    p_sys->p_ext = NULL;
    p_sys->p_frame = NULL;
    p_sys->pp_last = &p_sys->p_frame;
    p_sys->b_frame_slice = VLC_FALSE;

    p_sys->i_dts = p_sys->i_pts = 0;

    p_sys->i_frame_rate = 1;
    p_sys->i_frame_rate_base = 1;
    p_sys->b_seq_progressive = VLC_TRUE;
    p_sys->b_low_delay = VLC_TRUE;
    p_sys->i_seq_old = 0;

    p_sys->i_temporal_ref = 0;
    p_sys->i_picture_type = 0;
    p_sys->i_picture_structure = 0x03; /* frame */
    p_sys->i_top_field_first = 0;
    p_sys->i_repeat_first_field = 0;
    p_sys->i_progressive_frame = 0;
    p_sys->b_inited = 0;

    p_sys->i_interpolated_dts = 0;
    p_sys->i_old_duration = 0;
    p_sys->i_last_ref_pts = 0;

    return VLC_SUCCESS;
}

/*****************************************************************************
 * Close:
 *****************************************************************************/
static void Close( 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 );

    if( p_sys->p_seq )
    {
        block_Release( p_sys->p_seq );
    }
    if( p_sys->p_ext )
    {
        block_Release( p_sys->p_ext );
    }
    if( p_sys->p_frame )
    {
        block_ChainRelease( p_sys->p_frame );
    }

    free( p_sys );
}

/*****************************************************************************
 * Packetize:
 *****************************************************************************/
static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    block_t       *p_pic;

    if( pp_block == NULL || *pp_block == NULL )
    {
        return NULL;
    }

    if( (*pp_block)->i_flags & BLOCK_FLAG_DISCONTINUITY )
    {
        p_sys->i_state = STATE_NOSYNC;
        if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
        p_sys->p_frame = NULL;
        p_sys->pp_last = &p_sys->p_frame;
        p_sys->b_frame_slice = VLC_FALSE;
        block_Release( *pp_block );
        return NULL;
    }

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

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

        case STATE_NOSYNC:
            if( block_FindStartcodeFromOffset( &p_sys->bytestream,
                    &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
            {
                p_sys->i_state = STATE_NEXT_SYNC;
            }

            if( p_sys->i_offset )
            {
                block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
                p_sys->i_offset = 0;
                block_BytestreamFlush( &p_sys->bytestream );
            }

            if( p_sys->i_state != STATE_NEXT_SYNC )
            {
                /* Need more data */
                return NULL;
            }

            p_sys->i_offset = 1; /* To find next startcode */

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

            /* Find the next startcode */
            if( block_FindStartcodeFromOffset( &p_sys->bytestream,
                    &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
            {
                /* Need more data */
                return NULL;
            }

            /* Get the new fragment and set the pts/dts */
            p_pic = block_New( p_dec, p_sys->i_offset );
            block_BytestreamFlush( &p_sys->bytestream );
            p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
            p_pic->i_dts = p_sys->bytestream.p_block->i_dts;

            block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
                            p_pic->i_buffer );

            /* don't reuse the same timestamps several times */
            if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
            {
                /* We have a picture start code */
                p_sys->bytestream.p_block->i_pts = 0;
                p_sys->bytestream.p_block->i_dts = 0;
            }

            p_sys->i_offset = 0;

            /* Get picture if any */
            if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
            {
                p_sys->i_state = STATE_NOSYNC;
                break;
            }