FFmpeg/libavformat/flvenc.c

/*
 * FLV encoder.
 * Copyright (c) 2003 The FFmpeg Project.
 *
 * 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"

#undef NDEBUG
#include <assert.h>

typedef struct FLVContext {
    int hasAudio;
    int hasVideo;
    int reserved;
} FLVContext;

static void put_be24(ByteIOContext *pb, int value)
{
    put_byte(pb, (value>>16) & 0xFF );
    put_byte(pb, (value>> 8) & 0xFF );
    put_byte(pb, (value>> 0) & 0xFF );
}

static int get_audio_flags(AVCodecContext *enc){
    int flags = 0x02;

    switch (enc->sample_rate) {
        case    44100:
            flags |= 0x0C;
            break;
        case    22050:
            flags |= 0x08;
            break;
        case    11025:
            flags |= 0x04;
            break;
        case     8000: //nellymoser only
        case     5512: //not mp3
            flags |= 0x00;
            break;
        default:
            return -1;
    }

    if (enc->channels > 1) {
        flags |= 0x01;
    }
    
    switch(enc->codec_id){
    case CODEC_ID_MP3:
        flags |= 0x20;
        break;
    case 0:
        flags |= enc->codec_tag<<4;
        break;
    default:
        return -1;
    }
    
    return flags;
}

static int flv_write_header(AVFormatContext *s)
{
    ByteIOContext *pb = &s->pb;
    FLVContext *flv = s->priv_data;
    int i;

    flv->hasAudio = 0;
    flv->hasVideo = 0;

    put_tag(pb,"FLV");
    put_byte(pb,1);
    put_byte(pb,0); // delayed write
    put_be32(pb,9);
    put_be32(pb,0);
    
    for(i=0; i<s->nb_streams; i++){
        AVCodecContext *enc = &s->streams[i]->codec;
        av_set_pts_info(s->streams[i], 24, 1, 1000); /* 24 bit pts in ms */
        if(enc->codec_tag == 5){
            put_byte(pb,8); // message type
            put_be24(pb,0); // include flags
            put_be24(pb,0); // time stamp
            put_be32(pb,0); // reserved
            put_be32(pb,11); // size
            flv->reserved=5;
        }
        if(enc->codec_type == CODEC_TYPE_AUDIO && get_audio_flags(enc)<0)
            return -1;
    }

    return 0;
}

static int flv_write_trailer(AVFormatContext *s)
{
    int64_t file_size;
    int flags = 0;

    ByteIOContext *pb = &s->pb;
    FLVContext *flv = s->priv_data;

    file_size = url_ftell(pb);
    flags |= flv->hasAudio ? 4 : 0;
    flags |= flv->hasVideo ? 1 : 0;
    url_fseek(pb, 4, SEEK_SET);
    put_byte(pb,flags);
    url_fseek(pb, file_size, SEEK_SET);
    return 0;
}

static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    ByteIOContext *pb = &s->pb;
    AVCodecContext *enc = &s->streams[pkt->stream_index]->codec;
    FLVContext *flv = s->priv_data;
    int size= pkt->size;
    int flags;

//    av_log(s, AV_LOG_DEBUG, "type:%d pts: %lld size:%d\n", enc->codec_type, timestamp, size);
    
    if (enc->codec_type == CODEC_TYPE_VIDEO) {
        put_byte(pb, 9);
        flags = 2; // choose h263
        flags |= pkt->flags & PKT_FLAG_KEY ? 0x10 : 0x20; // add keyframe indicator
        flv->hasVideo = 1;
    } else {
        assert(enc->codec_type == CODEC_TYPE_AUDIO);
        flags = get_audio_flags(enc);
        
        assert(size);

        put_byte(pb, 8);

        // We got audio! Make sure we set this to the global flags on closure
        flv->hasAudio = 1;
    }

    put_be24(pb,size+1); // include flags
    put_be24(pb,pkt->pts);
    put_be32(pb,flv->reserved);
    put_byte(pb,flags);
    put_buffer(pb, pkt->data, size);
    put_be32(pb,size+1+11); // reserved

    put_flush_packet(pb);
    return 0;
}

static AVOutputFormat flv_oformat = {
    "flv",
    "flv format",
    "video/x-flashvideo",
    "flv",
    sizeof(FLVContext),
#ifdef CONFIG_MP3LAME
    CODEC_ID_MP3,
#else // CONFIG_MP3LAME
    CODEC_ID_NONE,
#endif // CONFIG_MP3LAME
    CODEC_ID_FLV1,
    flv_write_header,
    flv_write_packet,
    flv_write_trailer,
};

int flvenc_init(void)
{
    av_register_output_format(&flv_oformat);
    return 0;
}