ffmpeg生成带关键帧头信息的flv文件(一)

普通flv文件头信息中不带关键帧信息,在网页播放器中播放时,seek速度很慢,为了加快flv的seek速度,我们可以在flv的头信息中写入关键帧信息.
主要方法为;在写头信息时预留一定的位置用来写关键帧信息,在写包时包关键帧信息先保存起来,等到写文件结束时,根据需要把保存的关键帧信息写到预留的头信息中.

/*
* FLV muxer
* Copyright (c) 2003 The FFmpeg Project
*
* This file is part of FFmpeg.
*
* FFmpeg 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 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "stdafx.h"
#include "vxtempl.h"
extern "C"
{
#include "libavutil/intreadwrite.h"
#include "libavutil/intfloat.h"
#include "avformat.h"
#include "flv.h"
#include "internal.h"
#include "avc.h"
#include "metadata.h"
#include "libavutil/dict.h"

#undef NDEBUG
#include

static const ***CodecTag flv_video_codec_ids[] = {
{CODEC_ID_FLV1, FLV_CODECID_H263 },
{CODEC_ID_H263, FLV_CODECID_REALH263},
{CODEC_ID_MPEG4, FLV_CODECID_MPEG4 },
{CODEC_ID_FLASHSV, FLV_CODECID_SCREEN},
{CODEC_ID_FLASHSV2, FLV_CODECID_SCREEN2},
{CODEC_ID_VP6F, FLV_CODECID_VP6 },
{CODEC_ID_VP6, FLV_CODECID_VP6 },
{CODEC_ID_H264, FLV_CODECID_H264 },
{CODEC_ID_NONE, 0}
};

static const ***CodecTag flv_audio_codec_ids[] = {
{CODEC_ID_MP3, FLV_CODECID_MP3 >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_PCM_U8, FLV_CODECID_PCM >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_PCM_S16BE, FLV_CODECID_PCM >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_PCM_S16LE, FLV_CODECID_PCM_LE >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_ADPCM_SWF, FLV_CODECID_ADPCM >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_AAC, FLV_CODECID_AAC >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_NELLYMOSER, FLV_CODECID_NELLYMOSER >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_SPEEX, FLV_CODECID_SPEEX >> FLV_AUDIO_CODECID_OFFSET},
{CODEC_ID_NONE, 0}
};

#define MAX_FLV_KEY_FRAME 1500

typedef struct FLVContext {
int reserved;
double framerate;

int64_t duration_offset;
int64_t duration;
int64_t datasize_offset;
int64_t datasize;
int64_t videosize_offset;
int64_t videosize;
int64_t audiosize_offset;
int64_t audiosize;
int64_t filesize_offset;

int64_t delay; ///< first dts delay (needed for ***C & Speex)

int acurframeindex;

int64_t lasttimestamp_offset;
double lasttimestamp;
int64_t lastkeyframetimestamp_offset;
double lastkeyframetimestamp;
int64_t lastkeyframelocation_offset;
int64_t lastkeyframelocation;

int64_t filepositions_offset;
CVxArray filepositions;
int64_t filetimes_offset;
CVxArray<double> filetimes;

int64_t filetimesend_Pos;
int64_t datastart_offset;
} FLVContext;

typedef struct FLVStreamContext {
int64_t last_ts; ///< last timestamp for each stream
} FLVStreamContext;

static int get_audio_flags(***CodecContext *enc){
int flags = (enc->bits_per_coded_sample == 16) ? FLV_SAMPLESSIZE_16BIT : FLV_SAMPLESSIZE_8BIT;

if (enc->codec_id == CODEC_ID_AAC) // specs force these parameters
return FLV_CODECID_AAC | FLV_SAMPLERATE_44100HZ | FLV_SAMPLESSIZE_16BIT | FLV_STEREO;
else if (enc->codec_id == CODEC_ID_SPEEX) {
if (enc->sample_rate != 16000) {
av_log(enc, ***_LOG_ERROR, "flv only supports wideband (16kHz) Speex audio\n");
return -1;
}
if (enc->channels != 1) {
av_log(enc, ***_LOG_ERROR, "flv only supports mono Speex audio\n");
return -1;
}
return FLV_CODECID_SPEEX | FLV_SAMPLERATE_11025HZ | FLV_SAMPLESSIZE_16BIT;
} else {
switch (enc->sample_rate) {
case 44100:
flags |= FLV_SAMPLERATE_44100HZ;
break;
case 22050:
flags |= FLV_SAMPLERATE_22050HZ;
break;
case 11025:
flags |= FLV_SAMPLERATE_11025HZ;
break;
case 16000: //nellymoser only
case 8000: //nellymoser only
case 5512: //not mp3
if(enc->codec_id != CODEC_ID_MP3){
flags |= FLV_SAMPLERATE_SPECIAL;
break;
}
default:
av_log(enc, ***_LOG_ERROR, "flv does not support that sample rate, choose from (44100, 22050, 11025).\n");
return -1;
}
}

if (enc->channels > 1) {
flags |= FLV_STEREO;
}

switch(enc->codec_id){
case CODEC_ID_MP3:
flags |= FLV_CODECID_MP3 | FLV_SAMPLESSIZE_16BIT;
break;
case CODEC_ID_PCM_U8:
flags |= FLV_CODECID_PCM | FLV_SAMPLESSIZE_8BIT;
break;
case CODEC_ID_PCM_S16BE:
flags |= FLV_CODECID_PCM | FLV_SAMPLESSIZE_16BIT;
break;
case CODEC_ID_PCM_S16LE:
flags |= FLV_CODECID_PCM_LE | FLV_SAMPLESSIZE_16BIT;
break;
case CODEC_ID_ADPCM_SWF:
flags |= FLV_CODECID_ADPCM | FLV_SAMPLESSIZE_16BIT;
break;
case CODEC_ID_NELLYMOSER:
if (enc->sample_rate == 8000) {
flags |= FLV_CODECID_NELLYMOSER_8KHZ_MONO | FLV_SAMPLESSIZE_16BIT;
} else if (enc->sample_rate == 16000) {
flags |= FLV_CODECID_NELLYMOSER_16KHZ_MONO | FLV_SAMPLESSIZE_16BIT;
} else {
flags |= FLV_CODECID_NELLYMOSER | FLV_SAMPLESSIZE_16BIT;
}
break;
case 0:
flags |= enc->codec_tag<<4;
break;
default:
av_log(enc, ***_LOG_ERROR, "codec not compatible with flv\n");
return -1;
}

return flags;
}

static void put_amf_string(***IOContext *pb, const char *str)
{
size_t len = strlen(str);
avio_wb16(pb, len);
avio_write(pb, (const unsigned char *)str, len);
}

static void put_avc_eos_tag(***IOContext *pb, unsigned ts) {
avio_w8(pb, FLV_TAG_TYPE_VIDEO);
avio_wb24(pb, 5); /* Tag Data Size */
avio_wb24(pb, ts); /* lower 24 bits of timestamp in ms*/
avio_w8(pb, (ts >> 24) & 0x7F); /* MSB of ts in ms*/
avio_wb24(pb, 0); /* StreamId = 0 */
avio_w8(pb, 23); /* ub[4] FrameType = 1, ub[4] CodecId = 7 */
avio_w8(pb, 2); /* ***C end of sequence */
avio_wb24(pb, 0); /* Always 0 for ***C EOS. */
avio_wb32(pb, 16); /* Size of FLV tag */
}

static void put_amf_dword_array(***IOContext *pb, DWORD dw)
{
avio_w8(pb, AMF_DATA_TYPE_ARRAY);
avio_wb32(pb, dw);
}

static void put_amf_double(***IOContext *pb, double d)
{
avio_w8(pb, AMF_DATA_TYPE_NUMBER);
avio_wb64(pb, av_double2int(d));
}

static void put_amf_byte(***IOContext *pb, BYTE abyte)
{
avio_w8(pb, abyte);
}

static void put_amf_bool(***IOContext *pb, int b) {
avio_w8(pb, AMF_DATA_TYPE_BOOL);
avio_w8(pb, !!b);
}

From: http://blog.chinaunix.net/uid-20718335-id-3194374.html