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• FFmpeg support for repeating last audiosample and videoframe when input stream stops or delivers corrupt data ?

  14 novembre 2017, par Vemund Kvam

  Our goal is to deliver on-the-fly packaged Live HLS and Mpeg DASH from a mpeg-ts multicast source.

  We use ffmpeg to transcode/mux the mpeg-ts input to ISMV (smooth streaming format) and transfer via http to Unified Origin running Apache.

  What we want to achieve is a constant ISMV stream to Unified Origin regardless of input stability.

  We have tried separating decoding and encoding by having two FFMPEG processes :

  1. Decodes "rawvideo" and "s16be" (audio) and sends to two python developed buffers that have the ability to repeat the last frame/sample if no input is provided.
  2. Uses the two buffer as input (over tcp) and encode/mux to ISMV.

  This solution seems to solve the stability issue, but synchronising a/v and knowing when to provide repeated frames instead of live frames seems to be impossible. We have so far assumed that ffmpeg requires a continuous input stream to produce any output if the input is not or can not be provided, output stops.

  Does FFmpeg have built in functionality for repeating a/v when the input stream either stops delivering data or delivers corrupt data ?

  Is there any industry standard way to deal with unstable input ?

• FFMPEG Interframe to intraframe without 'converting' or losing data

  11 août 2017, par Domenick Simpson

  I’m new to this so I apologise I couldn’t find the answer after searching.

  I am just ripping some video content for my film show-reel (specifically the Lego movie bluray) and came across some issues. When using ’makeMKV’ and ’xMedia Recode’ to perform a lossless transfer of the video data into an mp4 container I am getting artifacts in After Effects due to the interframe encoding of this bluray in H264 format. This doesn’t seem to be a problem with the Lego Batman movie bluray for some reason, maybe it uses Interframe. Anyway, some frames have block artifacts etc when editing / cutting shots.

  Is there a way to convert this original MP4 stream into the same format without losing data / into an intraframe mp4 for editing purposes ?

  I have used various re-encoding methods to H264 and prores that don’t result in block artifacts but result in less quality and different colourspace, and, higher file sizes.

  In FFMPEG I also tried exporting the mp4 as a png sequence but I assume due to the conversion of YUV to RGB I am getting quite noticeable differences in reds and gamma. I’d also prefer to keep this as a H264 or single video file if possible. Full disclosure, I tried various conversion types rgb24 etc to retain colour info but this didn’t work either.

• Fast movie creation using MATLAB and ffmpeg

  24 février 2018, par hyiltiz

  I have some time series data that I would like to create into movies. The data could be 2D (about 500x10000) or 3D (500x500x10000). For 2D data, the movie frames are simply line plot using plot, and for 3D data, we can use surf, imagesc, contour etc. Then we create a video file using these frames in MATLAB, then compress the video file using ffmpeg.

  To do it fast, one would try not to render all the images to display, nor save the data to disk then read it back again during the process. Usually, one would use getframe or VideoWriter to create movie in MATLAB, but they seem to easily get tricky if one tries not to display the figures to screen. Some even suggest plotting in hidden figures, then saving them as images to disk as .png files, then compress them using ffmpeg (e.g. with x265 encoder into .mp4). However, saving the output of imagesc in my iMac took 3.5s the first time, then 0.5s after. I also find it not fast enough to save so many files to disk only to ask ffmpeg to read them again. One could hardcopy the data as this suggests, but I am not sure whether it works regardless of the plotting method (e.g. plot, surf etc.), and how one would transfer data over to ffmpeg with minimal disk access.

  This is similiar to this, but immovie is too slow. This post 3 is similar, but advocates writing images to disk then reading them (slow IO).