Cuando decodifico cuadros desde un archivo avi y luego los decodifico en x264 y los guardo en un archivo mp4, los fps del archivo de salida siempre son 12,800. Por lo tanto, el archivo se reproduce muy rápido. Pero, cuando guardo el codificado en cuadros h264 en formato avi y no mp4, el fps es como quería - 25.

¿Cual podría ser el problema?

Aquí el código que escribí en 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;
}