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Some questions about rtmp server channels #32

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scbizu opened this issue May 2, 2017 · 5 comments
Closed

Some questions about rtmp server channels #32

scbizu opened this issue May 2, 2017 · 5 comments

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@scbizu
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scbizu commented May 2, 2017

I read the example code in example > rtmp_server_channels > main.go , but I am really confused about the meaning of delaygop waitkey framedrop delayskip cachegop ,could U add some explanation about this words ? BTW, Thanks for developing such a wonderful streaming lib ~

@scbizu scbizu changed the title Some question about rtmp server channels Some questions about rtmp server channels May 2, 2017
@scbizu
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scbizu commented May 2, 2017

And does joy4 support ffmpeg -s ?

@acls
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acls commented May 2, 2017

I'm fairly new to video decoding, so somebody correct me if I get anything wrong.

If you know what GOP is, then the meaning of those variables will make more sense. GOP (Group of pictures) is a collection of video frames. It starts with a key frame, which is a frame that doesn't need other frames in order to be decoded. Other non-key frames make up the changes between the key frames and rely on other frames to be decoded.

Given that description of GOP, this is what I think they mean:

  • cachegop - sets the maximum number of GOPs to cache
  • delaygop - seek backwards N key frames/GOPs up to the size set withcachegop
  • waitkey - wait for a key frame, so that the first frame you get is a key frame. This will fix image artifacts that you would get before the key frame arrives.
  • framedrop - drops every Nth frame that isn't a key frame. This will cause image artifacts until the next key frame arrives.
  • delayskip - skips entire GOP if there is a delay (I'm not 100% sure if this is correct)

@scbizu
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scbizu commented May 3, 2017

Hi, acls .Firstly,Thanks for your explanation about the GOP,I also found it in wikipedia,I will try these options later.And have U tried to stream multiple channels ,I mean that can joy4's rtmp server solution deal with the streaming with multiple resolution,I read cgo/ffmpeg > video.go,but I do not see any implementation~ I am also new to video decoding as well as ffmpeg lol~

@acls
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acls commented May 5, 2017

As far as I know joy4 doesn't handle multiple resolutions.

@scbizu
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scbizu commented May 7, 2017

hmmm .. I finally use FFmpeg to do a forwarding via exec package ,However, I think it is not elegant enough at all(need ffmpeg dependency), Anyway, Thanks. @acls

@scbizu scbizu closed this as completed May 7, 2017
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