当我从 avi 文件解码帧然后在 x264 中解码它们并保存到 mp4 文件时，输出文件的 fps 始终为 12,800。因此文件播放速度非常快。但是，当我将编码的 h264 帧保存为 avi 格式而不是 mp4 时，fps 就是我想要的 - 25。
可能是什么问题呢？
这是我在VS2010中编写的代码：
#include "stdafx.h"
#include "inttypes.h"
extern "C" {
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libavutil/avutil.h"
#include <libswscale/swscale.h>
#include <libavutil/opt.h>
#include <libswscale/swscale.h>
#include <libavutil/imgutils.h>
}
#include <iostream>
using namespace std;
int main(int argc, char* argv[])
{
const char* inFileName = "C:\\000227_C1_GAME.avi";
const char* outFileName = "c:\\test.avi";
const char* outFileType = "avi";
av_register_all();
AVFormatContext* inContainer = NULL;
if(avformat_open_input(&inContainer, inFileName, NULL, NULL) < 0)
exit(1);
if(avformat_find_stream_info(inContainer, NULL) < 0)
exit(1);
// Find video stream
int videoStreamIndex = -1;
for (unsigned int i = 0; i < inContainer->nb_streams; ++i)
{
if (inContainer->streams[i] && inContainer->streams[i]->codec &&
inContainer->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
{
videoStreamIndex = i;
break;
}
}
if (videoStreamIndex == -1) exit(1);
AVFormatContext* outContainer = NULL;
if(avformat_alloc_output_context2(&outContainer, NULL, outFileType, outFileName) < 0)
exit(1);
// ----------------------------
// Decoder
// ----------------------------
AVStream const *const inStream = inContainer->streams[videoStreamIndex];
AVCodec *const decoder = avcodec_find_decoder(inStream->codec->codec_id);
if(!decoder)
exit(1);
if(avcodec_open2(inStream->codec, decoder, NULL) < 0)
exit(1);
// ----------------------------
// Encoder
// ----------------------------
AVCodec *encoder = avcodec_find_encoder(AV_CODEC_ID_H264);
if(!encoder)
exit(1);
AVStream *outStream = avformat_new_stream(outContainer, encoder);
if(!outStream)
exit(1);
avcodec_get_context_defaults3(outStream->codec, encoder);
// Construct encoder
if(outContainer->oformat->flags & AVFMT_GLOBALHEADER)
outStream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
outStream->codec->coder_type = AVMEDIA_TYPE_VIDEO;
outStream->codec->pix_fmt = AV_PIX_FMT_YUV420P;
outStream->codec->width = inStream->codec->width;
outStream->codec->height = inStream->codec->height;
outStream->codec->codec_id = encoder->id;
outStream->codec->bit_rate = 500000;
//outStream->codec->rc_min_rate = 600000;
//outStream->codec->rc_max_rate = 800000;
outStream->codec->time_base.den = 25;
outStream->codec->time_base.num = 1;
outStream->codec->gop_size = 250; // Keyframe interval(=GOP length). Determines maximum distance distance between I-frames
outStream->codec->keyint_min = 25; // minimum GOP size
outStream->codec->max_b_frames = 3;//16; // maximum number of B-frames between non-B-frames
outStream->codec->b_frame_strategy = 1; // decides the best number of B-frames to use. Default mode in x264.
outStream->codec->scenechange_threshold = 40;
outStream->codec->refs = 6; // abillity to reference frames other than the one immediately prior to the current frame. specify how many references can be used.
outStream->codec->qmin = 0;//10;
outStream->codec->qmax = 69;//51;
outStream->codec->qcompress = 0.6;
outStream->codec->max_qdiff = 4;
outStream->codec->i_quant_factor = 1.4;//0.71;
outStream->codec->refs=1;//3;
outStream->codec->chromaoffset = -2;
outStream->codec->thread_count = 1;
outStream->codec->trellis = 1;
outStream->codec->me_range = 16;
outStream->codec->me_method = ME_HEX; //hex
outStream->codec->flags2 |= CODEC_FLAG2_FAST;
outStream->codec->coder_type = 1;
if(outStream->codec->codec_id == AV_CODEC_ID_H264)
{
av_opt_set(outStream->codec->priv_data, "preset", "slow", 0);
}
// Open encoder
if(avcodec_open2(outStream->codec, encoder, NULL) < 0)
exit(1);
// Open output container
if(avio_open(&outContainer->pb, outFileName, AVIO_FLAG_WRITE) < 0)
exit(1);
//close_o
AVFrame *decodedFrame = avcodec_alloc_frame();
if(!decodedFrame)
exit(1);
AVFrame *encodeFrame = avcodec_alloc_frame();
if(!encodeFrame)
exit(1);
encodeFrame->format = outStream->codec->pix_fmt;
encodeFrame->width = outStream->codec->width;
encodeFrame->height = outStream->codec->height;
if(av_image_alloc(encodeFrame->data, encodeFrame->linesize,
outStream->codec->width, outStream->codec->height,
outStream->codec->pix_fmt, 1) < 0)
exit(1);
av_dump_format(inContainer, 0, inFileName,0);
//Write header to ouput container
avformat_write_header(outContainer, NULL);
AVPacket decodePacket, encodedPacket;
int got_frame, len;
while(av_read_frame(inContainer, &decodePacket)>=0)
{
if (decodePacket.stream_index == videoStreamIndex)
{
len = avcodec_decode_video2(inStream->codec, decodedFrame, &got_frame, &decodePacket);
if(len < 0)
exit(1);
if(got_frame)
{
av_init_packet(&encodedPacket);
encodedPacket.data = NULL;
encodedPacket.size = 0;
if(avcodec_encode_video2(outStream->codec, &encodedPacket, decodedFrame, &got_frame) < 0)
exit(1);
if(got_frame)
{
if (outStream->codec->coded_frame->key_frame)
encodedPacket.flags |= AV_PKT_FLAG_KEY;
encodedPacket.stream_index = outStream->index;
if(av_interleaved_write_frame(outContainer, &encodedPacket) < 0)
exit(1);
av_free_packet(&encodedPacket);
}
}
}
av_free_packet(&decodePacket);
}
av_write_trailer(outContainer);
avio_close(outContainer->pb);
avcodec_free_frame(&encodeFrame);
avcodec_free_frame(&decodedFrame);
avformat_free_context(outContainer);
av_close_input_file(inContainer);
return 0;
}