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Oliver Rath
on Nov 18, 2008 at 8:44:58 am

Hi all,

in our company we want to live encode a HD1080-videostream from a "Decklink HD Extreme 2" to MPEG-4 while parallel showing a small preview window. This should be done on an Intel Q9650 (QuadCore 3,0GHz/core), 2 GB RAM and Windows XP SP3.

Unfortunately, the resulting videos in all of our tests aren't really good; the preview and the video both have visible frameloss (about 18-20 fps instead of 25 fps). While encoding, the cpu usage is about 65-70%, so this can't be the reason.

Our DirectShow-filtergraph contains two "Avi decompressors", which we suspect of being the main reason for the frameloss; the codec is very good and very fast (see graph below). The "Avi decompressor"s are inserted behind the capture source and convert the HDYC colorspace coming from the card to a color format the encoder and the video renderer understand (UYVY or something else).

Is there any way to bypass the "Avi decompressor"s? What about the "Blackmagic Design Decoder (DMO)"-filter, it understands HDYC too, but if we insert it in our graph, we only get a black screen and the encoded video's size remains at 64 KB... what are we doing wrong? (The video renderer is not connectable to the "Blackmagic Design Decoder (DMO)" either).

Any help would be gladly appreciated!

Here's our filtergraph:

"Video Capture Source"
-> "Smart Tee"
->(capture) "Avi Decompressor"
-> "Encoder"
-> "Avi Mux"
-> "FileWriter"
->(preview) "Avi Decompressor"
-> "Video Renderer"


- Oliver

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