Recherche avancée

Sur d’autres sites (5776)

• Grab partial .mp4 video from onlline source

  28 juillet 2016, par Flemingjp

  I want to be able to grab a partial mp4 file from an online source so I can produce quick thumbnails.

  My idea was to pull a patial mp4 file from a http request using the header

  Range: 'bytes=1000-'

  However when I parse the data it doesn’t have the mp4 container therefore is corrupt. In Firefox it handles this easily as seeking to an unloaded part of the video is very quick.

  How can I pull partial mp4 clips ? For example from here I could get a clip that is 0:28-0:30

• ffmpeg audio synch issue - fractional framerate

  29 mars 2013, par JoeCitizen

  We are working on an Android app which uses the ffmpeg library via JNI to edit the frames of a video while keeping size, codec etc the same.

  We are having an issue where the audio of the output video is getting out of sync with the video. We believe this is because some input videos have a frame rate which isn't a whole number e.g 25.66 fps and our output will be at 25fps. We have tried to change the time_base field of the output codec to keep the precision i.e by multiply the numerator and denominator but it makes the output frame rate ridiculously high.

  Does anyone know how to force ffmpeg to use the exact same output frame rate as the one it reads in ? We have not found a way to output videos with a fractional frame rate.

  Example of setting up the output codec :

      c =                 st->codec;
  
      c->codec_id =       codec_id;
  
      c->codec_type =     AVMEDIA_TYPE_VIDEO;
  
      c->bit_rate =       inputCodecCtx->bit_rate;
  
      c->width =          inputCodecCtx->width;
  
      c->height =         inputCodecCtx->height;
  
  
  
      c->time_base.num =   1000;
  
      c->time_base.den =  (int)(fps*1000);//fps of the input video *1000 to keep precision
  
  
  
      c->gop_size =       inputCodecCtx->gop_size;
  
      c->pix_fmt =        inputCodecCtx->pix_fmt;
  
  
  
  
  
  
  
      static int write_video_frame(AVFormatContext *oc, AVStream *st, AVFrame *newpict, double fps)
  
      {
  
          int             ret = 0;
  
          AVCodecContext* c = st->codec;
  
  
  
          AVPacket pkt;
  
          av_init_packet(&pkt);
  
  
  
          if (pkt.pts != AV_NOPTS_VALUE)
  
          {
  
              pkt.pts =  av_rescale_q(c->coded_frame->pts, c->time_base, st->time_base);
  
  
  
          }
  
          if (pkt.dts != AV_NOPTS_VALUE)
  
  
  
  
  
          {
  
              pkt.dts = av_rescale_q(c->coded_frame->pts, c->time_base, st->time_base);
  
          }
  
  
  
  .....
  
  }

• av_read_frame function in ffmpeg in android always returning packet.stream_index as 0

  31 juillet 2013, par droidmad

  I am using the following standard code pasted below (ref : http://dranger.com/ffmpeg/) to use ffmpeg in android using ndk. My code is working fine in ubuntu 10.04 using gcc compiler. But I am facing an issue in android.The issue is av_read_frame(pFormatCtx, &packet) is always returning packet.stream_index=0. I have tested my code with various rtsp urls and I have the same behaviour in all cases. I do not have any linking or compiling issues as everything seems to be working fine except this issue. I am trying to solve this from last 2 days but I am stuck badly.Please point me in right direction.

  #include 
  
  #include <android></android>log.h>
  
  
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  
  
  #include 
  
  #define DEBUG_TAG "mydebug_ndk"
  
  
  
  jint Java_com_example_tut2_MainActivity_myfunc(JNIEnv * env, jobject this,jstring myjurl) {
  
    AVFormatContext *pFormatCtx = NULL;
  
    int             i, videoStream;
  
    AVCodecContext  *pCodecCtx = NULL;
  
    AVCodec         *pCodec = NULL;
  
    AVFrame         *pFrame = NULL;
  
    AVPacket        packet;
  
    int             frameFinished;
  
  
  
    AVDictionary    *optionsDict = NULL;
  
    struct SwsContext *sws_ctx = NULL;
  
  
  
    jboolean isCopy;
  
    const char * mycurl = (*env)->GetStringUTFChars(env, myjurl, &amp;isCopy);
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:p2: [%s]", mycurl);
  
  
  
    // Register all formats and codecs
  
    av_register_all();
  
    avformat_network_init();
  
    // Open video file
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:before_open");
  
  
  
    if(avformat_open_input(&amp;pFormatCtx, mycurl, NULL, NULL)!=0)
  
        return -1;
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "start: %d\t%d\n",pFormatCtx->raw_packet_buffer_remaining_size,pFormatCtx->max_index_size);
  
  
  
    (*env)->ReleaseStringUTFChars(env, myjurl, mycurl);
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:before_stream");
  
    // Retrieve stream information
  
    if(avformat_find_stream_info(pFormatCtx, NULL)&lt;0)
  
        return -1;
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:after_stream");
  
    // Find the first video stream
  
    videoStream=-1;
  
    for(i=0; inb_streams; i++)
  
        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
  
          videoStream=i;
  
          break;
  
        }
  
    if(videoStream==-1)
  
        return -1; // Didn&#39;t find a video stream
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:after_videostream");
  
    // Get a pointer to the codec context for the video stream
  
    pCodecCtx=pFormatCtx->streams[videoStream]->codec;
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:after_codec_context");
  
  
  
    // Find the decoder for the video stream
  
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:after_decoder");
  
  
  
    if(pCodec==NULL)
  
        return -1;
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:found_decoder");
  
  
  
    // Open codec
  
    if(avcodec_open2(pCodecCtx, pCodec, &amp;optionsDict)&lt;0)
  
        return -1;
  
    // Allocate video frame
  
    pFrame=avcodec_alloc_frame();
  
    sws_ctx = sws_getContext(pCodecCtx->width,pCodecCtx->height,pCodecCtx->pix_fmt,pCodecCtx->width,
  
          pCodecCtx->height,PIX_FMT_YUV420P,SWS_BILINEAR,NULL,NULL,NULL);
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:before_while");
  
  
  
    int count=0;
  
    while(av_read_frame(pFormatCtx, &amp;packet)>=0) {
  
          __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "entered while: %d   %d   %d\n", packet.duration,packet.stream_index,packet.size);
  
  
  
        if(packet.stream_index==videoStream) {
  
            // Decode video frame
  
            //break;
  
            avcodec_decode_video2(pCodecCtx, pFrame, &amp;frameFinished,&amp;packet);
  
            __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:in_while");
  
            if(frameFinished) {
  
                __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:gng_out_of_while");
  
                  break;
  
            }
  
        }
  
  
  
        // Free the packet that was allocated by av_read_frame
  
        av_free_packet(&amp;packet);
  
        if(++count>1000)
  
           return -2; //infinite while loop
  
    }
  
    __android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:after_while");
  
  
  
    // Free the YUV frame
  
    av_free(pFrame);
  
    // Close the codec
  
    avcodec_close(pCodecCtx);
  
    // Close the video file
  
    avformat_close_input(&amp;pFormatCtx);
  
  
  
    return 0;
  
  
  
  }