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Thread: Setting the keyframe interval in TC-1

  1. #1
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    Setting the keyframe interval in TC-1

    I haven't been able to find any recent documentation on interval keyframes.

    It appears that the Tricaster default keyframe interval is 3-frames. Is this still true, and if yes is there a way to change this to every 2 frames in the TC-1?

  2. #2
    'the write stuff' SBowie's Avatar
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    I'm sorry, not clear on the context - are you referring to keyframes in the context of the export module, streaming config, or something else?
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    Happy to provide more context. I'm referring to the changing how often a keyframe appears on the stream. It appears that the default Tricaster setting is every 3 frames. Changing it to every 2 frames should help with audio sync issues I'm experiencing with a webcast platform.

    The only documentation I've found that references what I want to change is at the following URL but may be out of date: ftp://ftp.newtek.com/pub/download/Fo...orkflow-v2.pdf

    On page 7 it says:

    5. On line 38, under flashmedialiveencoder_profile / encode / advanced, change the keyframe frequency from 3 seconds to 2 seconds; Use Save As and choose a name for this file; in our example we might use “YouTube 720 2048k”. Save it in a folder other than the TriCaster directory.

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    'the write stuff' SBowie's Avatar
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    Quote Originally Posted by boyler View Post
    I'm referring to the changing how often a keyframe appears on the stream. It appears that the default Tricaster setting is every 3 frames. Changing it to every 2 frames should help with audio sync issues I'm experiencing with a webcast platform.
    OK, thanks. Depending on who I ask around here, I get differing answers, but two things they agree on: First, in all recent TriCasters, the streaming output is created in hardware and this value is no longer editable. Second, they doubt that this is the cause of an audio sync issue.

    It would seem likely that if it was, we'd have heard quite a lot about it from unhappy users. Audio sync can be a thorny issue, and it's arguably more complex with streaming than local broadcast - but if you explain what you're seeing, and exactly where the issue is visible, folks might have some suggestions.
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    Steve - Thank you for confirming that these values are no longer editable.

    I agree that this is a thorny issue, and I also agree that this is unlikely the cause of the audio sync issues. I will provide more visibility into the sync issues tied to the keyframes in the future if/when possible.

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    It would be nice to have control with an advanced parameters section where we could put in the various commands such as keyframe distance. In my case I do multi bitrate streaming and my segment sizes are at 10 seconds. Not the end of the world but 3 second key frames means the segment system chooses between 9 seconds and 12 seconds. I was also told by one publishing group that the TC1 was using Variable bitrate vs Constant bitrate which is generally accepted as being more efficient but if you are trying to pass through the stream as the top bitrate the variability could causes some segments to exceed the advertised bitrate. This was feed back from flo hoops when I did an event for them late last year. I was apparently the first TC1 publishing directly to them.

    Thanks. We confirm receipt and have both video and audio. Our server seems to be unable to detect specifically you video and audio data rates. Are you using VBR (variable bit rate) encoding?
    To try and address this they sent me a Tricaster.xml file that they provide all their other tricaster users (8000s i guess) which contains the settings they expect including resolution, video keyframe distance, video bitrate, audio bitrate etc. When I imported the file on the TC1 it brought in the URL for rtmp publishing and it appeared to ignore all of the video config. This kind of makes sense in that you have 2 encoding engines that could each do one video stream as defined, but then separately you could push it to many locations (publish points without video config). So when I used the import at the publishing side the only valid data was the server url and stream name. I don't think the video config section has an import feature and from your comments it wouldn't matter as these items are no longer configurable? Where they ever? It appears they were back in the day maybe.

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    Back when we were using our T40 V1 to stream to Twitch I had to write an XML for the T40 to properly stream to Twitch with the proper framerate or else it was quite laggy.
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    Quote Originally Posted by Stream View Post
    Back when we were using our T40 V1 to stream to Twitch I had to write an XML for the T40 to properly stream to Twitch with the proper framerate or else it was quite laggy.
    Current products have a native Twitch Streaming Plugin.
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