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• FFmpeg : how to use C++ code to change the frame rate of a video file ?

  27 mars 2014, par user1914692

  I know it would be easier to use FFmpeg commands to change the frame rate of a video file.
  But anyway, if I want to do it in C++ code, and use FFmpeg libraries, how could I do it ?

  I think I should've be able to find out the clue in the source code.
  Just before proceeding, I hope there would be some good introductions or examples.

• Decoding audio w/ ffmpeg error on Android

  14 août 2012, par stranded

  Well, I knew I was going out of my comfort zone when I decided to try and decode audio using ffmpeg on Android but now I will have to admit that I'm stranded.
  It took me many days to just build ffmpeg for Android. Roman's10 guide did not work for me but finally things started looking up, thanks to this tutorial. So because of Dmitry's help I managed to build the armeabi version (not armeabi-v7) for my phone (LG P500) and everything basic works.

  But when I try to use avcodec_decode_audio3() things go downhill :( Never before have I felt so close to making things work (after all it seems to be only one line that is troublesome)
  but unable to though. I've read many questions here on SO that have brought me closer to the goal. Googling, on the other hand, has had limited results - making questions here the only fruit.

  Yes, I know ! I ramble. But I can't help it, I'm only trying to explain in detail where I'm stuck and how I got there. So without further ado I bring you the code :

  NATIVE CODE :

  #include 
  
  #include <android></android>log.h>
  
  
  
  #include "libavcodec/avcodec.h"
  
  #include "libavformat/avformat.h"
  
  
  
  #define LOG_TAG "mylib"
  
  #define LOGI(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
  
  #define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
  
  
  
  #define INBUFF_SIZE 4096
  
  #define AUDIO_INBUFF 20480
  
  #define AUDIO_REFILL_SIZE 4096
  
  
  
  jint Java_com_nothingworks_for_me_MainActivity_decode(JNIEnv * env, jobject this, jstring jfilename){
  
      const char *filename = (*env)->GetStringUTFChars(env, jfilename, NULL);
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int audioStream;
  
      int out_size, len, i;
  
      FILE *f, *outfile;
  
      uint8_t *outbuf;
  
      uint8_t inbuf[AUDIO_INBUFF + FF_INPUT_BUFFER_PADDING_SIZE];
  
      AVPacket avpkt;
  
      AVFormatContext *pFormatCtx;
  
  
  
      av_register_all();
  
      avcodec_init();
  
      av_init_packet(&amp;avpkt);
  
  
  
      if(av_open_input_file(&amp;pFormatCtx, filename, NULL, 0, NULL)!=0)
  
      {
  
          LOGE("Can&#39;t open file &#39;%s&#39;\n", filename);
  
          return 1;
  
      }
  
      else
  
      {
  
          LOGI("File was opened\n");
  
          LOGI("File &#39;%s&#39;, Codec %s",
  
                  pFormatCtx->filename,
  
                  pFormatCtx->iformat->name
  
          );
  
      }
  
  
  
      if (av_find_stream_info(pFormatCtx) &lt; 0){
  
          LOGE("Can&#39;t find stream info");
  
      }
  
      audioStream = -1;
  
      for (i = 0; i &lt; pFormatCtx->nb_streams; i++) {
  
          if (pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO) {
  
              audioStream = i;
  
              break;
  
          }
  
      }
  
  
  
      if (audioStream == -1) {
  
          LOGE("Didn&#39;t find stream!");
  
      }
  
      c = pFormatCtx->streams[audioStream]->codec;
  
  
  
      codec = avcodec_find_decoder(c->codec_id);
  
      if (!codec) {
  
          LOGE("Unsupported Codec!");
  
      }
  
  
  
      c= avcodec_alloc_context();
  
  
  
      /* open it */
  
      if (avcodec_open(c, codec) &lt; 0) {
  
          LOGE("Can&#39;t open codec");
  
          exit(1);
  
      }
  
  
  
      outbuf = av_malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE * 2);
  
  
  
      f = fopen(filename, "rb");
  
      if (!f) {
  
          LOGE("Can&#39;t open file");
  
          exit(1);
  
      }
  
  
  
      /* decode until eof */
  
      avpkt.data = inbuf;
  
      avpkt.size = fread(inbuf, 1, AUDIO_INBUFF, f);
  
      LOGI("avpkt.size %d", avpkt.size);
  
  
  
      while (avpkt.size > 0) {
  
          out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE * 2; 

  THINGS GO WRONG HERE ! avcodec_decode_audio3() The code continues from ▲ to ▼ :

          len = avcodec_decode_audio3(c, (int16_t *)outbuf, &out_size, &avpkt);
  
          LOGI("data_size %d len %d", out_size, len);
  
          if (len < 0) {
  
              LOGE("Error while decoding");
  
              exit(1);
  
          }
  
          if (out_size > 0) {
  
  
  
          }
  
          avpkt.size -= len;
  
          avpkt.data += len;
  
          if (avpkt.size < AUDIO_REFILL_SIZE) {
  
              /* Refill the input buffer, to avoid trying to decode
  
               * incomplete frames. Instead of this, one could also use
  
               * a parser, or use a proper container format through
  
               * libavformat. */
  
              memmove(inbuf, avpkt.data, avpkt.size);
  
              avpkt.data = inbuf;
  
              len = fread(avpkt.data + avpkt.size, 1,
  
                      AUDIO_INBUFF - avpkt.size, f);
  
              if (len > 0)
  
                  avpkt.size += len;
  
          }
  
      }
  
      fclose(f);
  
      free(outbuf);
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      return 0;
  
  }

  ---

  What happens is that avcodec_decode_audio3() returns -1 and that's pretty much it :(
  I have no idea what to do next. I can't find much info about this and I only started fiddling with C less than two weeks ago so your guidance is my only hope now [play dramatic sound]. Hope someone can shed a little light on this mystery.

  Ohh ! And the native code is some kind of a hybrid between what I have found here on SO, like this and this, and the ffmpeg example. On the java side I only have a call to this native method and pass it string which is the path to a MP3 song on my droid. I don't use AudioTrack or anything else in my java code yet 'cause I'm only trying to get the decoding to work for now.

  -Drama Queen OUT !

• FFMPEG FTP is not working

  16 mai 2014, par SENTHIL SARAVANAN

  I want convert video files using FFMPEG and upload into my server using FTP. For this i used the following ffmpeg command

  ffmpeg -i C:\Users\sen\Desktop\sss\input.mov ftp://root:xxxxxxxxxxx@xxx.xxx.xxx.24/output.flv

  But ffmpeg shows like authentication failed, i hope i give valid server credentials only. Please refer the ffmpeg screen for more detail

  How can solve this issue.