Latency when viewing live streams about omxplayer HOT 10 CLOSED

If someone could point me to some info on how the buffering is supposed to work I would be happy to look into this issue. Really just looking for some pointers on where to start looking :)

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Does running with 0.1 instead of 0.5 for fifo/buffer sizes help?
When you run with "-s" what values does "V:" and "S:" stabilise at?

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0.1 doesn't work, here is the lowest values I have found that do work. It is odd that the audio_fifo tag is in seconds where the rest are in MB.
./vsmedia -s --video_fifo 0.25 --video_queue 0.25 --audio_fifo 2 --audio_queue 0.05 --threshold 0.1 udp://@192.168.1.128:5006

This yields a latency of about 7 seconds
Status
M:21895958 V: 1.69s 240k/ 240k A: 0.73 1.02s/ 2.00s Cv: 235k Ca: 24k

This shows the input cache basically full, with the output clock being presumably driven by trying to keep the output audio fifo centered at 50%. But the video output buffer is too small for that, so these numbers don't make sense....

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V: = video_fifo in seconds (video_fifo is set via command line in MB, but 250Kb is not enough for 1.7s delay in 720p ???

m_player_video.GetDecoderBufferSize()-m_player_video.GetDecoderFreeSpace() / m_player_video.GetDecoderBufferSize() in Kb
What is decoder_buffer and why is it kept full?

A: = audio_fifo in seconds?

m_player_audio.GetDelay() / m_player_audio.GetCacheTotal() also in seconds?

CV = m_player_video.GetCached() in kb
ca = m_player_audio.GetCached() in kb

Audio is AAC 128kbps, so 16Kb would be 1 second of input audio. With a audio queue of 50Kb that should be 3.125 seconds ...

I guess I just don't understand how the buffers are allocated and used enough to know how to set the parameters.

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Ok, found the problem. FFMPEG is buffering all the data it uses for stream format analysis. Just have to add the flag below to correct (when opening the stream).

// discards the frames buffered during stream analysis
m_pFormatContext->flags |= AVFMT_FLAG_NOBUFFER;

That said, there are still more issues elsewhere in the pipe. I don't think the OMX clock adjustment is working properly...

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What file / line did you add the flag to to make FFMPEG not buffer the data?

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OMXReader.cpp

Insert it after this line
m_pFormatContext->flags |= AVFMT_FLAG_NONBLOCK;

However, you should only do this on live streams otherwise you can cutoff the start of files.

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Okay so that worked.

I am trying to use the PI as a low latency Video Decoder. Adding the NOBUFFER flag dropped the latency in half to about 2 seconds.

Any recommendations on getting it even lower? I am trying to get it below 400 ms if it is possible.

Thanks

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See #55

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I believe this is resolved. Please report additional issues on
#55

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