TeraDek quality issue

Conversations around originating a webcast for conference, including cameras and mixers.
aclawson
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TeraDek quality issue

Postby aclawson » Fri Oct 23, 2015 5:59 am

As an A/V source for my testing I use the satellite feed rather than the feed from the camera, pointing at an empty chapel.

I notice that when the satellite stream is panning across a packed conference center the stream goes blocky, then stabilizes back to crisp and clear when focused on the speaker.

Since our SCs won't involve panning across the chapel, and the camera blacks out as it jumps to a new angle this isn't expected to be an issue, but it is a curious oddity. Has anybody else noticed this/can they replicate? Any thoughts as to why it would be behaving like this?

lajackson
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Re: TeraDek quality issue

Postby lajackson » Fri Oct 23, 2015 9:16 am

aclawson wrote:Has anybody else noticed this/can they replicate? Any thoughts as to why it would be behaving like this?

For me, it is usually a sign of low bandwidth. When the picture is relatively stable, it is not necessary to send down a lot of video information. When a scene is moving, such as panning across the Tabernacle Choir), the entire picture needs to be resent constantly to keep up.

Some software compensates by pixelating. Other software compensates by dropping complete frames, resulting in a jerky, stop-action-type motion. Another method leaves the picture a little less sharp for a few seconds until things settle down and the video catches up.

Lack of bandwidth is usually the culprit.

aclawson
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Re: TeraDek quality issue

Postby aclawson » Fri Oct 23, 2015 9:44 am

We are on Comcast Business Class and can easily sustain 4MB/s on the uplink, and I was the only person in the building at the time except for the patriarch and he wasn't doing anything online. I'll have to go out there again and watch the logs I suppose, but we shouldn't be hitting any bandwidth issues.

russellhltn
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Re: TeraDek quality issue

Postby russellhltn » Fri Oct 23, 2015 9:45 am

lajackson wrote:For me, it is usually a sign of low bandwidth. When the picture is relatively stable, it is not necessary to send down a lot of video information. When a scene is moving, such as panning across the Tabernacle Choir), the entire picture needs to be resent constantly to keep up.

Correct. A "jump cut" just requires one new frame and then normal compression kicks in. But if you've got something that continuously changes every pixel, that gives the compression system a major headache. I've seen even the satellite system pixilate at the end of Music and the Spoken Word when the camera shot a close up of a running stream.
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aclawson
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Re: TeraDek quality issue

Postby aclawson » Sun Oct 25, 2015 11:12 am

I just ran a test stream to my meetinghouse and was getting the pixelation problem. Since it is the test video directly from the church it probably is not a sending side bandwidth issue. My meetinghouse is showing a speedtest speed of 15.11 so it shouldn't be a bandwidth issue on the local side, either.

craiggsmith
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Re: TeraDek quality issue

Postby craiggsmith » Fri Oct 30, 2015 8:30 am

Whe testing make sure you give the receiving side 10 to 15 minutes for the bandwidth to adjust; it starts out really low (<100k) and gradually increases it up to 900k if the receiving side can handle it.
Craig
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