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• Stream OpenGL framebuffer over HTTP (via FFmpeg)

  17 juin 2016, par mOfl

  I have an OpenGL application of which rendered images need to be streamed over internet to mobile clients. Previously, it sufficed to simply record the rendering into a video file, which is already working, and now this should be extended to subsequent streaming.

  What is working right now :

  • Render a scene to an OpenGL framebuffer object
  • Capture the FBO content using NvIFR
  • Encode it to H.264 using NvENC (no CPU round trip required)
  • Download the encoded frame to host memory as a byte array
  • Append this frame to a video file

  None of this steps involves FFmpeg or any other library so far. I now want to replace the last step with "Stream the current frame’s byte array over internet" and I assume that using FFmpeg and FFserver would be a reasonable choice for this. Am I correct ? If not, what would be the proper way ?

  If so, how do I approach this within my C++ code ? As pointed out, the frame is already encoded. Also, there is no sound or other stuff, simply a H.264 encoded frame as byte array that is updated irregularly and should be converted into a steady video stream. I assume that this would be FFmpeg’s job and that the subsequent streaming via FFserver would be simple from there. What I don’t know is how to feed my data to FFmpeg in the first place, as all FFmpeg tutorials I found (in a non-exhaustive search) work on a file or webcam/capture device as data source, not volatile data in main memory.

  The file mentioned above that I am already able to create is a C++ file stream to which I append each single frame, meaning that different framerates of video and rendering are not treated correctly. This also needs to be taken care of at some point.

  Can somebody point me in the right direction ? Can I forward data from my application to FFmpeg to build a proper video feed without writing to the hard disk ? Tutorials are greatly appreciated. By the way FFmpeg/FFserver is not mandatory. If you have a better idea for streaming of OpenGL framebuffer contents, I’m eager to know.

• HLS implementation with FFmpeg

  6 juin 2017, par Joseph K

  I am trying to implement HLS using FFmpeg for transcoding + segmenting but have been facing a couple of issues that have been bugging me for the past week.

  Issue

  Webserver currently receives live MP4 fragments being recorded on-the-go and needs to take care of transcoding and segmentation.

  As mp4 fragments are being received, they need to be encoded. Then segmented. If i run a segmenter (be it ffmpeg or apple mediastreamsegmenter), every mp4 fragment is being treated as a VOD by itself and I’m not being able to integrate them as part of a larger live event implementation.

  I thought of a solution where every time I receive an mp4 fragment, I first use fmpeg to concatenate it with previous ones to form the larger mp4 that I then pass to be segmented for HLS. That did not work either because the entire stream has to be re-segmented each and every time and existing TS fragments replaced by new ones that are similar yet shifted in time.

  Implementation 1

  ffmpeg -re -i fragmentX.mp4 -b:v 118k -b:a 32k -vcodec copy -preset:v veryfast -acodec aac -strict -2 -ac 2 -f mpegts -y fragmentX.ts

  I manage the m3u8 manifest on my own, deleting old fragments and appending new ones.

  When validating the stream, I find it stacked with EXT-X-DISCONTINUITY tags making the stream unwatchable.

  Implementation 2

  First combine latest fragment with overall.mp4

  ffmpeg -i "concat:newfragment.mp4|existing.mp4" -c copy overall.mp4

  Then pass the combination to ffmpeg for HLS segmentation

  ffmpeg -re -i overall.mp4 -ac 2 -r 20 -vcodec libx264 -b:v 318k -preset:v veryfast -acodec aac -strict -2 -b:a 32k -hls_time 2 -hls_list_size 3 -hls_allow_cache 0 -hls_base_url /Users/JosephKalash/Desktop/test/350/ -hls_segment_filename ’350/fragment%03d.ts’ -hls_flags delete_segments 350/index.m3u8

  Concatenation is not perfect and there are noticeable glitches where the fragments are supposed to be stitched. Segmentation replaces older fragments and the manifest is rewritten as if it’s a new HLS stream every time ffmpeg is called.

  I cannot figure out how to get this to work properly.

  Any ideas ?

• HLS implementation with FFmpeg

  10 août 2015, par Joseph K

  I am trying to implement HLS using FFmpeg for transcoding + segmenting but have been facing a couple of issues that have been bugging me for the past week.

  Issue

  Webserver currently receives live MP4 fragments being recorded on-the-go and needs to take care of transcoding and segmentation.

  As mp4 fragments are being received, they need to be encoded. Then segmented. If i run a segmenter (be it ffmpeg or apple mediastreamsegmenter), every mp4 fragment is being treated as a VOD by itself and I’m not being able to integrate them as part of a larger live event implementation.

  I thought of a solution where every time I receive an mp4 fragment, I first use fmpeg to concatenate it with previous ones to form the larger mp4 that I then pass to be segmented for HLS. That did not work either because the entire stream has to be re-segmented each and every time and existing TS fragments replaced by new ones that are similar yet shifted in time.

  Implementation 1

  ffmpeg -re -i fragmentX.mp4 -b:v 118k -b:a 32k -vcodec copy -preset:v veryfast -acodec aac -strict -2 -ac 2 -f mpegts -y fragmentX.ts

  I manage the m3u8 manifest on my own, deleting old fragments and appending new ones.

  When validating the stream, I find it stacked with EXT-X-DISCONTINUITY tags making the stream unwatchable.

  Implementation 2

  First combine latest fragment with overall.mp4

  ffmpeg -i "concat:newfragment.mp4|existing.mp4" -c copy overall.mp4

  Then pass the combination to ffmpeg for HLS segmentation

  ffmpeg -re -i overall.mp4 -ac 2 -r 20 -vcodec libx264 -b:v 318k -preset:v veryfast -acodec aac -strict -2 -b:a 32k -hls_time 2 -hls_list_size 3 -hls_allow_cache 0 -hls_base_url /Users/JosephKalash/Desktop/test/350/ -hls_segment_filename ’350/fragment%03d.ts’ -hls_flags delete_segments 350/index.m3u8

  Concatenation is not perfect and there are noticeable glitches where the fragments are supposed to be stitched. Segmentation replaces older fragments and the manifest is rewritten as if it’s a new HLS stream every time ffmpeg is called.

  I cannot figure out how to get this to work properly.

  Any ideas ?