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• Merge multiple videos without using command line-FFMPEG [on hold]

  19 avril 2018, par Valgrind1691

  I am developing an android application which has video processing features involved.
  For video processing I have been working with FFMPEG library. As for now ffmpeg is directly being consumed by android and the processing is being done by
  framing commands and executing it using ffmpeg executable running in the background.
  This approach has two drawbacks :

  1) Video Processing time is huge even after trying ultrafast and other options to reduce processing

  2) APK size is large

  For solving two major problems we seek c/c++ native implementation for video processing by using the ffmpeg code.
  The C/C++ code will be cross compiled for android and iOS platforms and provided to mobile platform as a library (.so file in case of Android)
  The .so file will have

  1. jni for communication between Android(java) and c/c+

  2. c++ code for functionality implementation of video processing. All
     the video processing i.e scaling, transcoding, merging,
     cropping etc will be done by C/C++ code.

  I have a query around the C/C++ side , how can we use ffmpeg not to process using command line rather we can define algorithms for the process. Transcoding, muxing etc I have achieved looking into the examples of ffmpeg but I am still unable to figure out algorithm for merging of multiple(upto 6) videos in a single video file.
  I have looked into every question posted in this context and none helped.
  Can someone help me merge videos using source code of ffmpeg without using command line ? Any help is appreciated.

• ffmpeg is setting start_time to a negative value on output

  16 mai 2016, par Éric

  We’ve been using an old version of ffmpeg for a while and now we need to upgrade to a more recent version (e.g. 2.6) and we have issues with it while converting .mov to .mp4.

  For instance I have a .mov video file that has two streams, video and audio, both with start_time=0 and when I convert it using :

  ffmpeg -i my_file.mov my_file.mp4

  the output mp4 has an audio stream with start_time=-0.021333.

  The FORMAT section, as shown by ffprobe -show_format -show_streams my_file.mp4
  also has start_time=-0.021333

  The previous version of ffmpeg we were using didn’t have this issue...

  When we play the output mp4 file in a web browser using < video > it’s all good while playing but if we pause the video and seek here and there we notice that all the frames are off by 1. The first frame is duplicated and the last frame is missing !

  In other words :

  dom.currentTime = 0 shows the first frame
  
  dom.currentTime = 1/24 (fps is 24) shows the first frame again
  
  dom.currentTime = 2/24 shows the second frame instead of the third frame
  
  dom.currentTime = 3/24 shows the third frame instead of the fourth frame
  
  ...

  We believe this is caused by the field start_time=-0.021333

  This is a major issue for us...

  It’s repro on chrome and firefox but somehow safari is not having issues with this...

  After googling this we found that we’re not the only one with this issue but it’s not clear what the solution is.

  Someone suggested to use the "-c:a copy" arguments and it worked on some files but gave an error on some others :

  Could not write header for output file #0 (incorrect codec parameters ?) : Invalid argument

  So this doesn’t seem to be a robust solution...

  Any help would be appreciated.

• Solution for VB6 to broadcast Webcam

  11 juillet 2014, par vantrung -cuncon

  Sorry, I know VB6 is decades ago, but I’m in a situation that I have to use VB6 to deliver live webcam stream beetween 2 PC in Server - Client Model program. Vb6-code holds the connection then I have no choice but to transfer all data via that connection.

  I’ve tried weeks for this, uncountable approaches but went to nowhere.
  My efforts focused on 3 major approaches :

  1/ Use ffmpeg to record live webcam as ".avi" file on hard disk, transfer parts of file to other end & play it. But I’ve stucked with a media-player that can play a "being written" avi file.

  Windows Media Player control told me "file already in use..." & VLC Plugin can’t even be added to VB6 (axvlc.dll).

  2/ Use ffmpeg to save live webcam as avi file, transfer each bit of that file to the other end, then in other end, extract 24 images / second from the avi to display continously in a picture box.
  This approach is ok except that my hard disk get fulled of images in a time of wink and my program get very slow before hanging.

  3/ Use ffmpeg to stream the live webcam to a rtp-port like this :

  ffmpeg -f dshow -i video="Lenovo EasyCamera" -vcodec mpeg2video -pix_fmt yuv422p -f rtp -an rtp://224.1.2.3:8191

  I’ve successfully watch the stream in VLC, but VLC(axvlc.dll) refused to be integrated into ancient VB6. And more important, I don’t know how to redirect/reroute the rtp stream to other PC with VB6.

  Any one please light me up ? (Any 3rd party component is welcomed)