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• DXGI Desktop Duplication : encoding frames to send them over the network

  13 novembre 2016, par prazuber

  I’m trying to write an app which will capture a video stream of the screen and send it to a remote client. I’ve found out that the best way to capture a screen on Windows is to use DXGI Desktop Duplication API (available since Windows 8). Microsoft provides a neat sample which streams duplicated frames to screen. Now, I’ve been wondering what is the easiest, but still relatively fast way to encode those frames and send them over the network.

  The frames come from AcquireNextFrame with a surface that contains the desktop bitmap and metadata which contains dirty and move regions that were updated. From here, I have a couple of options :

  1. Extract a bitmap from a DirectX surface and then use an external library like ffmpeg to encode series of bitmaps to H.264 and send it over RTSP. While straightforward, I fear that this method will be too slow as it isn’t taking advantage of any native Windows methods. Converting D3D texture to a ffmpeg-compatible bitmap seems like unnecessary work.
  2. From this answer : convert D3D texture to IMFSample and use MediaFoundation’s SinkWriter to encode the frame. I found this tutorial of video encoding, but I haven’t yet found a way to immediately get the encoded frame and send it instead of dumping all of them to a video file.

  Since I haven’t done anything like this before, I’m asking if I’m moving in the right direction. In the end, I want to have a simple, preferably low latency desktop capture video stream, which I can view from a remote device.

  Also, I’m wondering if I can make use of dirty and move regions provided by Desktop Duplication. Instead of encoding the frame, I can send them over the network and do the processing on the client side, but this means that my client has to have DirectX 11.1 or higher available, which is impossible if I would want to stream to a mobile platform.

• How to record 720p videos without dropping frames in Android

  20 novembre 2015, par user2880229

  I compiled ffmpeg and h264 libraries for android using NDK.
  I am recording videos using the muxing.c example from the ffmpeg library. Everything works correct (still haven’t worked on the audio) but the camera is dropping frames and it takes around 100ms to save each frame, which is unacceptable.

  I have also tried making a queue and saving them into another thread (let’s call it B) but at the end I need to wait for around 120 seconds because the background thread (B)is still recording the frames.

  Is there a workaround for this issue, besides reducing the video size ? Ideally I would like to save the frames in real time, at least reduce the saving time. Is it just that Android is incapable of doing this ? .

• How can I create a c++ console application which makes use of an open source c project

  2 octobre 2018, par Bogdan Daniel

  I’ve been playing around with a compiled version of https://github.com/FFmpeg/FFmpeg. But it has some problems, during the closing of an opened stream using avio_close(it takes a really long time to close it).

  I’ve been trying to understand what could go wrong by reading through the implementation, but couldn’t find anything.

  What I would like to do, is to actually have a C++ console application which uses the c files and to debug them while running the code(using breakpoints and so on).

  Unfortunately I cannot find any information on how to set it up. Simply copying the files in a new console application is not enough.

  Thanks in advance for any suggestions.

  Edit : I can already see a closing vote. If this question is not appropriate for this website, I will delete it. But please point me in the right direction of where to post it.Although it is quite a general question, I believe that it is clear and enough information has been provided.

  Edit2 : Yes, I was a bit unclear about what I’m using.

  I’m using Visual Studio Community 2017 on Windows 10 for creating the C++ console application.

  Edit3 :

  Steps that I’ve taken into using the source files into my console application which was using the DLLs.

  1. Copy all of the contents of the FFmpeg-master to my console application
  2. Include all of them in the c++ console application project
  3. Run a build - takes forever and has infinite build errors( > 1000) - probably compiler related

  Edit4 :

  I have no actual errors with avio_close, it just takes too long to close the stream. What I found out when playing around with the settings is that when the fifo_size parameter is set, closing the stream is a lot faster depending on how small the set value is. And it sort of makes sense since fifo_size is related to the packet size, but I haven’t found out where in the code this size has an impact.

  fifo_size=units
  Set the UDP receiving circular buffer size, expressed as a number of packets with size of 188 bytes. If not specified defaults to 7*4096.

  Edit5 : I still haven’t found a way to compile the open source ffmpeg project into libs, dlls and pdbs. Am I the first one needing such files(seems unrealistic) ?
  The only tool capable of delivering those so far is vcpkg. The only problem is that it compiles the 3.3.3 version and the latest is 4.0.2 .

  I tried to modify the vcpkg\ports\ffmpeg\portfile.cmake file to include the latest version of ffmpeg, but it doesn’t build it.

  Are there any other suggestions ?