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• mp4 to hls ffmpeg during upload to Google storage

  13 février 2018, par Sofiia Vynnytska

  I have an API written on Java, which is used for uploading mp4 videos on front-end. We store those videos on google cloud and our application is running in google cloud. For Android clients, we need to convert uploaded videos to hls. Unfortunately, Google cloud does not have transcoder for videos and I need to convert video in another way. I found that ffmpeg can do this. But I cannot find a good solution for this and I need an advice.
  One of ideas is to deploy cloud function on google cloud, which will convert mp4 to hls after uploading video. Can I need to upload this m3u8 and ts videos to storage ? Will be this approach okay ? Is there any other possible solution ?

• FFMPEG : Displaying a white screen using ffplay via a custom decoder

  11 décembre 2013, par Zax

  I have created a dummy decoder, Here in its decode function, i would be assigning the output file pointer with a YUV420 data filled with 255 (i.e. a white screen).

  I also have a corresponding probe function for my dummy decoder, where it takes an dummy input file and based on some checking i return AVPROBE_SCORE_MAX. This probe section works perfectly fine and invokes my custom dummy decoder.

  The AVCodec structure of for my dummy decoder is as shown below :

  AVCodec ff_dummyDec_decoder = {
  
      .name           = "dummyDec",
  
      .type           = AVMEDIA_TYPE_VIDEO,
  
      .id             = AV_CODEC_ID_MYDEC,
  
      .priv_data_size = sizeof(MYDECContext),
  
      .pix_fmts       = (const enum AVPixelFormat[]) {AV_PIX_FMT_YUV420P},
  
      .init           = dummyDec_decode_init,
  
      .close          = dummyDec_decode_close,
  
      .decode         = dummyDec_decode_frame,
  
  };

  Where,

  .init -> is a pointer to a function that performs my decoder related initializations
  
  .close -> is a pointer to a function that frees all memory that was allocated during initialization
  
  .decode -> is pointer to a function that decodes a frame.

  The definitions for the above functions is shown below :

  #include 
  
  #include 
  
  #include "avcodec.h"
  
  
  
  unsigned char *yPtr=NULL;
  
  unsigned char *uPtr=NULL;
  
  unsigned char *vPtr=NULL;
  
  
  
  int memFlag=0;//If memFlag is zero then allocate memory for YUV data
  
  
  
  int width=416;//Picture width and height that i want to display in ffplay
  
  int height=240;
  
  
  
  static int dummyDec_decode_frame(AVCodecContext *avctx, void *data,
  
                               int *got_frame_ptr, AVPacket *avpkt)
  
  {
  
      AVFrame *frame=data; //make frame point to the pointer on which output should be mapped
  
      printf("\nDecode function entered\n");
  
      frame->width=width;
  
      frame->height=height;
  
      frame->format=AV_PIX_FMT_YUV420P;
  
  
  
      //initialize frame->linesize[] array
  
      avpicture_fill((AVPicture*)frame, NULL, frame->format,frame->width,frame->height);
  
  
  
      frame->data[0]=yPtr;
  
      frame->data[1]=uPtr;
  
      frame->data[2]=vPtr;
  
  
  
      *got_frame_ptr = 1;
  
  
  
      printf("\nGotFramePtr set to 1\n");
  
  
  
      return width*height+(width/2)*(height/2)+(width/2)*(height/2);//returning the amount of bytes being used
  
  }
  
  
  
  static int dummyDec_decode_init(AVCodecContext *avctx)
  
  {
  
      printf("\nDummy Decoders init entered\n");
  
  
  
      //Allocate memory for YUV data
  
      yPtr=(unsigned char*)malloc(sizeof(unsigned char*)*width*height);
  
      uPtr=(unsigned char*)malloc(sizeof(unsigned char*)*width/2*height/2);
  
      vPtr=(unsigned char*)malloc(sizeof(unsigned char*)*width/2*height/2);
  
  
  
      if(yPtr == NULL || uPtr ==NULL ||vPtr==NULL)
  
          exit(0);
  
  
  
      //set allocated memory with 255 i.e white color
  
     memset(yPtr,255,width*height);
  
     memset(uPtr,255,width/2*height/2);
  
     memset(vPtr,255,width/2*height/2);
  
  }
  
  
  
  static int dummyDec_decode_close(AVCodecContext *avctx)
  
  {
  
      free(yPtr);
  
      free(uPtr);
  
      free(vPtr);
  
  }

  From the dummyDec_decode_frame() function, i'm returning the number of bytes that are being used to display the white colour. Is this right ? Secondly, I have no parser for my decoder, because i'm just mapping a yuv buffer containing white data to AVFrame structure pointer.

  The command that i use for executing is :

  ./ffplay -vcodec dummyDec -i input.bin

  The output is an infinite loop with the following messages :

  dummyDec probe entered
  
  
  
  Dummy Decoders init entered
  
  
  
  Decode function entered
  
  
  
  GotFramePtr set to 1
  
  
  
  Decode function entered
  
  
  
  GotFramePtr set to 1
  
  
  
  Decode function entered
  
  
  
  GotFramePtr set to 1
  
  
  
  .
  
  
  
  .
  
  
  
  .(the last two messages keep repeating)

  Where is it i'm going wrong ? is it the absence of parser or something else ? I'm unable to proceed because of this. Please provide your valuable answers. Thanks in advance.

  —Regards

• Playing a custom avi data stream using QtMultimedia

  26 décembre 2015, par sbabbi

  I need to play back a custom AVI file that contains a classic video stream, an audio stream but also a custom data stream.

  The custom stream contains data that is visualized by some custom widgets ; those widgets only need that each custom frame is written in a buffer at the proper time.

  Our application is based on Qt, and already uses QMediaPlayer/QVideoWidget to play traditional videos, but the additional custom stream makes things more complicated, because AFAIK QMediaPlayer only plays the video/audio and ignores everything else.

  I would like to avoid to reinvent the entire qt-multimedia, but I am not sure how to make the best out of the available Qt classes.

  ---

  My ideas so far are :

  1. Write a custom media player class that demuxes and decodes the video using ffmpeg, implements the timing, uses QAudioOutput for playing the audio, produces a stream of QVideoFrames to be played on the video and write the custom data to some buffer for visualization.

     The problem : In order to avoid writing the code to rescale/convert the video frames, I would like to reuse QVideoWidget, but it seems to work only with the "real" QMediaPlayer.

  2. Demux the input file and feed QMediaPlayer with the AV streams.
     Demux the input with ffmpeg (possibly leaving the decoding to the Qt backend), have one QIODevice to retrieve only the video/audio streams from the input file and another one to retrieve the data stream. Play the video/audio with QMediaPlayer.

                   +-------+                          
     
                   | QFile |                          
     
                   +---^---+                          
     
                       |                              
     
                    inherits                          
     
                       |                              
     
             +--------------------+
     
             |    MyAviDemuxer    |
     
             |                    |
     
             |  holds a queue of  |
     
             |  demuxed packets   |
     
             +--------------------+
     
             |                    |
     
       readDataPacket      readVideoPacket
     
             |                    |
     
     +-------v--------+  +--------v-----------+            +-----------+
     
     | MyCustomReader |  | MyVideoAudioStream +--inherits--> QIODevice |
     
     +----------------+  +--------+-----------+            +-----------+
     
                                  |       
     
                               setMedia                  
     
                                  |                  
     
                          +-------v-------+           
     
                          | QMediaPlayer  |           
     
                          +---------------+           

     The problem : synchronize the timing of the data stream with QMediaPlayer, handle headers and metadata correctly.

  ---

  I am slightly inclined to option 1, just because it gives me more control, but I am wondering if I missed an easier solution (even Windows-only).