mpeg.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.10平台上编译为嵌入式图形界面操作系统。

/*
 * MPEG1/2 mux/demux
 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include "avformat.h"

#define MAX_PAYLOAD_SIZE 4096
#define NB_STREAMS 2

typedef struct {
    uint8_t buffer[MAX_PAYLOAD_SIZE];
    int buffer_ptr;
    uint8_t id;
    int max_buffer_size; /* in bytes */
    int packet_number;
    int64_t start_pts;
} StreamInfo;

typedef struct {
    int packet_size; /* required packet size */
    int packet_data_max_size; /* maximum data size inside a packet */
    int packet_number;
    int pack_header_freq;     /* frequency (in packets^-1) at which we send pack headers */
    int system_header_freq;
    int mux_rate; /* bitrate in units of 50 bytes/s */
    /* stream info */
    int audio_bound;
    int video_bound;
    int is_mpeg2;
    int is_vcd;
} MpegMuxContext;

#define PACK_START_CODE             ((unsigned int)0x000001ba)
#define SYSTEM_HEADER_START_CODE    ((unsigned int)0x000001bb)
#define SEQUENCE_END_CODE           ((unsigned int)0x000001b7)
#define PACKET_START_CODE_MASK      ((unsigned int)0xffffff00)
#define PACKET_START_CODE_PREFIX    ((unsigned int)0x00000100)
#define ISO_11172_END_CODE          ((unsigned int)0x000001b9)
  
/* mpeg2 */
#define PROGRAM_STREAM_MAP 0x1bc
#define PRIVATE_STREAM_1   0x1bd
#define PADDING_STREAM     0x1be
#define PRIVATE_STREAM_2   0x1bf


#define AUDIO_ID 0xc0
#define VIDEO_ID 0xe0

#ifdef CONFIG_ENCODERS
extern AVOutputFormat mpeg1system_mux;
extern AVOutputFormat mpeg1vcd_mux;
extern AVOutputFormat mpeg2vob_mux;

static int put_pack_header(AVFormatContext *ctx, 
                           uint8_t *buf, int64_t timestamp)
{
    MpegMuxContext *s = ctx->priv_data;
    PutBitContext pb;
    
    init_put_bits(&pb, buf, 128);

    put_bits(&pb, 32, PACK_START_CODE);
    if (s->is_mpeg2) {
        put_bits(&pb, 2, 0x1);
    } else {
        put_bits(&pb, 4, 0x2);
    }
    put_bits(&pb, 3, (uint32_t)((timestamp >> 30) & 0x07));
    put_bits(&pb, 1, 1);
    put_bits(&pb, 15, (uint32_t)((timestamp >> 15) & 0x7fff));
    put_bits(&pb, 1, 1);
    put_bits(&pb, 15, (uint32_t)((timestamp) & 0x7fff));
    put_bits(&pb, 1, 1);
    if (s->is_mpeg2) {
        /* clock extension */
        put_bits(&pb, 9, 0);
        put_bits(&pb, 1, 1);
    }
    put_bits(&pb, 1, 1);
    put_bits(&pb, 22, s->mux_rate);
    put_bits(&pb, 1, 1);
    if (s->is_mpeg2) {
        put_bits(&pb, 5, 0x1f); /* reserved */
        put_bits(&pb, 3, 0); /* stuffing length */
    }
    flush_put_bits(&pb);
    return pbBufPtr(&pb) - pb.buf;
}

static int put_system_header(AVFormatContext *ctx, uint8_t *buf)
{
    MpegMuxContext *s = ctx->priv_data;
    int size, rate_bound, i, private_stream_coded, id;
    PutBitContext pb;

    init_put_bits(&pb, buf, 128);

    put_bits(&pb, 32, SYSTEM_HEADER_START_CODE);
    put_bits(&pb, 16, 0);
    put_bits(&pb, 1, 1);
    
    rate_bound = s->mux_rate; /* maximum bit rate of the multiplexed stream */
    put_bits(&pb, 22, rate_bound);
    put_bits(&pb, 1, 1); /* marker */
    put_bits(&pb, 6, s->audio_bound);

    put_bits(&pb, 1, 1); /* variable bitrate */
    put_bits(&pb, 1, 1); /* non constrainted bit stream */
    
    put_bits(&pb, 1, 0); /* audio locked */
    put_bits(&pb, 1, 0); /* video locked */
    put_bits(&pb, 1, 1); /* marker */

    put_bits(&pb, 5, s->video_bound);
    put_bits(&pb, 8, 0xff); /* reserved byte */
    
    /* audio stream info */
    private_stream_coded = 0;
    for(i=0;i<ctx->nb_streams;i++) {
        StreamInfo *stream = ctx->streams[i]->priv_data;
        id = stream->id;
        if (id < 0xc0) {
            /* special case for private streams (AC3 use that) */
            if (private_stream_coded)
                continue;
            private_stream_coded = 1;
            id = 0xbd;
        }
        put_bits(&pb, 8, id); /* stream ID */
        put_bits(&pb, 2, 3);
        if (id < 0xe0) {
            /* audio */
            put_bits(&pb, 1, 0);
            put_bits(&pb, 13, stream->max_buffer_size / 128);
        } else {
            /* video */
            put_bits(&pb, 1, 1);
            put_bits(&pb, 13, stream->max_buffer_size / 1024);
        }
    }
    flush_put_bits(&pb);
    size = pbBufPtr(&pb) - pb.buf;
    /* patch packet size */
    buf[4] = (size - 6) >> 8;
    buf[5] = (size - 6) & 0xff;

    return size;
}

static int mpeg_mux_init(AVFormatContext *ctx)
{
    MpegMuxContext *s = ctx->priv_data;
    int bitrate, i, mpa_id, mpv_id, ac3_id;
    AVStream *st;
    StreamInfo *stream;

    s->packet_number = 0;
    s->is_vcd = (ctx->oformat == &mpeg1vcd_mux);
    s->is_mpeg2 = (ctx->oformat == &mpeg2vob_mux);
    
    if (s->is_vcd)
        s->packet_size = 2324; /* VCD packet size */
    else
        s->packet_size = 2048;
        
    /* startcode(4) + length(2) + flags(1) */
    s->packet_data_max_size = s->packet_size - 7;
    s->audio_bound = 0;
    s->video_bound = 0;
    mpa_id = AUDIO_ID;
    ac3_id = 0x80;
    mpv_id = VIDEO_ID;
    for(i=0;i<ctx->nb_streams;i++) {
        st = ctx->streams[i];
        stream = av_mallocz(sizeof(StreamInfo));
        if (!stream)
            goto fail;
        st->priv_data = stream;

        switch(st->codec.codec_type) {
        case CODEC_TYPE_AUDIO:
            if (st->codec.codec_id == CODEC_ID_AC3)
                stream->id = ac3_id++;
            else
                stream->id = mpa_id++;
            stream->max_buffer_size = 4 * 1024; 
            s->audio_bound++;
            break;
        case CODEC_TYPE_VIDEO:
            stream->id = mpv_id++;
            stream->max_buffer_size = 46 * 1024; 
            s->video_bound++;
            break;
        default:
            av_abort();
        }
    }

    /* we increase slightly the bitrate to take into account the
       headers. XXX: compute it exactly */
    bitrate = 2000;
    for(i=0;i<ctx->nb_streams;i++) {
        st = ctx->streams[i];
        bitrate += st->codec.bit_rate;
    }
    s->mux_rate = (bitrate + (8 * 50) - 1) / (8 * 50);
    
    if (s->is_vcd || s->is_mpeg2)
        /* every packet */
        s->pack_header_freq = 1;
    else
        /* every 2 seconds */
        s->pack_header_freq = 2 * bitrate / s->packet_size / 8;

    /* the above seems to make pack_header_freq zero sometimes */
    if (s->pack_header_freq == 0)
       s->pack_header_freq = 1;
    
    if (s->is_mpeg2)
        /* every 200 packets. Need to look at the spec.  */
        s->system_header_freq = s->pack_header_freq * 40;
    else if (s->is_vcd)
        /* every 40 packets, this is my invention */
        s->system_header_freq = s->pack_header_freq * 40;
    else
        s->system_header_freq = s->pack_header_freq * 5;
    
    for(i=0;i<ctx->nb_streams;i++) {
        stream = ctx->streams[i]->priv_data;
        stream->buffer_ptr = 0;
        stream->packet_number = 0;
        stream->start_pts = -1;
    }
    return 0;
 fail:
    for(i=0;i<ctx->nb_streams;i++) {
        av_free(ctx->streams[i]->priv_data);
    }
    return -ENOMEM;
}

/* flush the packet on stream stream_index */
static void flush_packet(AVFormatContext *ctx, int stream_index)
{
    MpegMuxContext *s = ctx->priv_data;
    StreamInfo *stream = ctx->streams[stream_index]->priv_data;
    uint8_t *buf_ptr;
    int size, payload_size, startcode, id, len, stuffing_size, i, header_len;
    int64_t timestamp;
    uint8_t buffer[128];
    
    id = stream->id;
    timestamp = stream->start_pts;

#if 0
    printf("packet ID=%2x PTS=%0.3f\n", 
           id, timestamp / 90000.0);
#endif

    buf_ptr = buffer;
    if (((s->packet_number % s->pack_header_freq) == 0)) {
        /* output pack and systems header if needed */
        size = put_pack_header(ctx, buf_ptr, timestamp);
        buf_ptr += size;
        if ((s->packet_number % s->system_header_freq) == 0) {
            size = put_system_header(ctx, buf_ptr);
            buf_ptr += size;
        }
    }
    size = buf_ptr - buffer;
    put_buffer(&ctx->pb, buffer, size);

    /* packet header */
    if (s->is_mpeg2) {
        header_len = 8;
    } else {
        header_len = 5;
    }
    payload_size = s->packet_size - (size + 6 + header_len);
    if (id < 0xc0) {
        startcode = PRIVATE_STREAM_1;
        payload_size -= 4;
    } else {
        startcode = 0x100 + id;
    }
    stuffing_size = payload_size - stream->buffer_ptr;
    if (stuffing_size < 0)
        stuffing_size = 0;

    put_be32(&ctx->pb, startcode);

    put_be16(&ctx->pb, payload_size + header_len);
    /* stuffing */
    for(i=0;i<stuffing_size;i++)
        put_byte(&ctx->pb, 0xff);

    if (s->is_mpeg2) {
        put_byte(&ctx->pb, 0x80); /* mpeg2 id */
        put_byte(&ctx->pb, 0x80); /* flags */
        put_byte(&ctx->pb, 0x05); /* header len (only pts is included) */
    }
    put_byte(&ctx->pb, 
             (0x02 << 4) | 
             (((timestamp >> 30) & 0x07) << 1) | 
             1);
    put_be16(&ctx->pb, (uint16_t)((((timestamp >> 15) & 0x7fff) << 1) | 1));
    put_be16(&ctx->pb, (uint16_t)((((timestamp) & 0x7fff) << 1) | 1));

    if (startcode == PRIVATE_STREAM_1) {
        put_byte(&ctx->pb, id);
        if (id >= 0x80 && id <= 0xbf) {
            /* XXX: need to check AC3 spec */
            put_byte(&ctx->pb, 1);
            put_byte(&ctx->pb, 0);
            put_byte(&ctx->pb, 2);
        }
    }

    /* output data */
    put_buffer(&ctx->pb, stream->buffer, payload_size - stuffing_size);
    put_flush_packet(&ctx->pb);
    
    /* preserve remaining data */
    len = stream->buffer_ptr - payload_size;
    if (len < 0) 
        len = 0;
    memmove(stream->buffer, stream->buffer + stream->buffer_ptr - len, len);
    stream->buffer_ptr = len;

    s->packet_number++;
    stream->packet_number++;
    stream->start_pts = -1;
}

static int mpeg_mux_write_packet(AVFormatContext *ctx, int stream_index,
                                 const uint8_t *buf, int size, int64_t pts)
{
    MpegMuxContext *s = ctx->priv_data;
    AVStream *st = ctx->streams[stream_index];
    StreamInfo *stream = st->priv_data;
    int len;
    
    while (size > 0) {
        /* set pts */
        if (stream->start_pts == -1) {
            stream->start_pts = pts;