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"Blocky/blurry" playback with high quality stream

Jul 14, 2011 11:05 AM

We have a 720p stream going into a Flash Media Encoder box that is sending live video through Akamai. Bandwidth is absolutely not the problem, but we are limited to around 250-500k bitrate just for cost reasons.

 

The content is essentially a radar of weather, 24 hours a day.

 

The stream looks great most of the time, but the problem is that when there's lots of moving content (a storm coming through the area) the entire stream gets blocky/blurry specifically at an interval equal to the number of seconds chosen for keyframe setting. Changing the keyframe to say, one second, just produces the same issues every second in stead of every six seconds (the default). Essentially, it looks fine up until the sixth second, when the entire stream turns to "mush" for about half a second.

 

Is there anything we can do here? Feel really limited by the options given by the encoder. We've tried changing lots of settings, but nothing has really worked other than very heavily increasing the bitrate, and even then, you can still see the block refresh, its just not as bad.

1094 Views   3 Replies   Latest reply: MatthewQuinn, Jul 15, 2011 3:16 AM
 
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  • Letmethink
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    1. Letmethink,
    Jul 14, 2011 9:17 PM   in reply to midimid
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    Are you using VP6 or H264? 500 kbps is less for 720p video. Which profile/level combination you are using?

     
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  • TimB_Kulabyte
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    2. TimB_Kulabyte,
    Jul 14, 2011 10:55 PM   in reply to midimid
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    Assuming H.264, 250-500k is not enough bitrate for the amount of data you need to push with a 1280x720 frame size.  What this looks like is exactly what you are seeing.  If nothing is moving on the screen it will look like you have a nice HD video, but as soon as there is movement you will have a large number of changes from frame to frame that need to be delivered and you do not have enough bandwidth to sufficiently communicate those changes.  At a 500k bitrate, I would suggest trying a 640x360 frame size for your content.

     

    Regards,

     

    Tim

     
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  • MatthewQuinn
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    3. MatthewQuinn,
    Jul 15, 2011 3:16 AM   in reply to TimB_Kulabyte
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    Agreed, thats no where near enough bitrate for a 720 stream, you should either follow Tim's advice or increase your bitrate to something over 2Mbps

     
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