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Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs

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Dave Kidd
Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs
on Sep 30, 2006 at 3:08:15 pm

Hi there,

I have been trying to resolve an issue with some WM videos that I have encoded for streaming. I use Canopus ProCoder with some custom settings I have set up and mostly they work fine with the footage I need to encode, but I'm having frame rate issues with some of the clips when the scenes are particularly 'busy'.

I have tried everything to force Canopus to put frames before quality, but there are times it still becomes jittery. The videos are either 4:3 or 16:9 encoded using Windows Media 9 video at 25fps, full PAL resolution (768x576) at 600kbps (total a/v) CBR 2 pass with audio 128k stereo, plus I have tried 2 pass VBR 600kbps with 80k assigned to audio, which does better with short burst of action but anything longer than a few seconds it struggles again and drops frames.

Unfortunately I can't compromise these encodes by dropping the number of frames, or the resolution, plus it must stay within the WMV9 technology, so I feel I have exhausted my options and knowledge here so I was hoping someone might be able to shed some light on the subject or even if there is a better encoder than Canopus for handling fast action scenes I would love to hear about.

Thanks in advance for any help or advice

Dave



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Craig Seeman
Re: Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs
on Oct 1, 2006 at 2:05:32 pm

I use Mac most of the time for my encodes but have done DV AVIs on WME on Windows often enough.

I will say your data rate is low for full frame size and frame rate. When doing CBR encodes adjust the Quality setting, sometimes called Smooth/Sharp to a low number (even Zero if needed).

I'd try dropping the frame size to 384x288 (maybe smaller depending on content). You'll get a much nicer looking encode.

VBR encoding won't work for streaming. Progressive download is another matter.

These data rates are VERY LOW for that frame size and frame rate IMHO.


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epontius
Re: Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs
on Oct 1, 2006 at 5:09:17 pm

Procoder does an excellent job of encoding WMV from my experience.
600k is pretty low for full frame and full frame rate that will result in a good quality smooth motion encode.
Most videos designed for streaming are going to be using a smaller frame size (perhaps half size) and frame rates less than full (15, 12, 24, etc...) allowing the media encoder more more bits to work with each frame. CBR encoding is also used for streaming. Since you are restricted to full frame, full frame rate and broadband bitrates, the quality of your encode will suffer. There are always tradeoffs.
Do you have the option of creating a smaller sized video for streaming and give the user an option of downloading a full frame/full frame rate, high quality bitrate (2k+) version to download for local playback?

Erik






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Dave Kidd
Re: Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs
on Oct 2, 2006 at 2:43:45 pm

Thank guys for getting back to me on the subject, really appreciate it. I think I've pushed the encoding to the limit in line with the constrictions I have over frame rates and frame size. The reason we encode like that is we noticed that when viewing a half size video full screen, this inherently induces pixellation, where as the bigger it is to start with, the better it looks full screen and for most of our common footage this works really well, as there isn't any quick cuts and fast action sequences. Seeing as many people are sporting displays bigger than 17" screen, we felt it was necessary to go down this route.

I initailly hoped that by setting the quality to zero, therefore forcing the encoding to bias towards frame rate over quailty this would be enough, but any busy scenes over a few seconds still become jittery and the only part cure for this was to make it a VRB encode and dropping the audio bitrate down further, but even this wasn't good enough to cope overall (plus it breaks a streaming golden rule!)

Due to the nature of the hosting system, we use have a one stop solution file which is used for both streaming and download, rather than separate files, so this is yet another constraint! I wasn't sure if there was some real low level option I could have tried to tweak the encoding even more than I have, but I'm guessing not from what you've both said, and that the long and short of it is that there are far too many parameters I'm having to adhere to which will never allow a perfect flowing video in any given situation (so in other words it's tough luck!)

I can't wait for the day when average global broadband data rates are into the 1000s of kbps, then I won't have this worry!

Regards

Dave



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Craig Seeman
Re: Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs
on Oct 2, 2006 at 3:07:15 pm

It's a longish shot but try changing the buffer size when doing CBR encoding.


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Charles Simonson
Re: Advice sought regarding frame rate issue when encoding WMV9 from DV AVIs
on Oct 3, 2006 at 3:41:47 am

Everyone is correct in that your bit rate is much too low for the resolution you are encoding to. I would say that anything at your resolution @ 1200kbps and below will experience dropped frames at 25fps. Almost every WM encoder that I know of is based on the same WM SDK, so this issue will not be resolved with other encoders available in this price range.

But some things that you could try are the following. 1.) Use the WVC1 advanced profile encoder (not the WMVA or WMV3 encoder). This encoder will take better advantage of your settings and while I would still expect dropped frames, there shouldn't be as many. 2.) Set your buffer size to something like 5 - 10 secs. This will affect how soon a client can tune into the stream, but it allow more bits to be allocated during your tricky sequences. 3.) Try setting your keyframes to 6 secs. A lower keyframe count will generate a better encode quality-wise, but this setting should help in making sure there are less dropped frames. 4.) Make sure you are selecting adaptive deinterlace and not just leaving this alone. 5.) I forget if ProCoder has a complexity setting for WMV, but if it does, then set that anywhere from to 0 - 2. With a decent enough bit rate and the above settings, a CBR encode should look pretty decent.


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