FPS too high when saving video in mp4 container

问题

When I decode frames from avi file and then decode them in x264 and save to mp4 file, the fps of the output file is always 12,800. Therefore the file is played very fast. But, when I save the encoded in h264 frames in avi format and not mp4, so the fps is as I wanted - 25.

What could be the problem?

Here the code I wrote in VS2010:

#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;
}

回答1:

The problem was with PTS and DTS of the packet. Before writing the packet to output( before av_interleaved_write_frame command) set PTS and DTS like this

if (encodedPacket.pts != AV_NOPTS_VALUE)
    encodedPacket.pts =  av_rescale_q(encodedPacket.pts, outStream->codec->time_base, outStream->time_base);
if (encodedPacket.dts != AV_NOPTS_VALUE)
    encodedPacket.dts = av_rescale_q(encodedPacket.dts, outStream->codec->time_base, outStream->time_base);

来源：https://stackoverflow.com/questions/13565062/fps-too-high-when-saving-video-in-mp4-container