Salmon Days: Format Wars

Go DivX!

Letters Several viewers complained about format incompatibilities when watching the trailer Salmon Days, our BOFH-inspired comedy epic. Most have been resolved. This correspondent questions the entire basis of our streaming video encoding efforts.



I noticed that your Salmon Days video trailer is trying to feed us, the general public, inferior video formats. Those inferior formats would be WMP, Real Player and Quick time. The superior format would be DivX4.02.

I know David Johns, the tech handling feedback for Salmon Days, thinks that WMP codec for video compression is the cat’s ass, but to be blunt he doesn’t know what he is talking about. Here is his response to my inquiry about why he hasn’t made Salmon Days available in DivX format.

"I don't agree - the codecs in WMP or Real8 actually give better quality for a given bitrate than DivX - it's just that most people don't encode WMP or Real at the kind of bitrates typically used by DivX (eg 1Mbit/sec) hence the widely believed quality difference. Not sure about the codecs used in Movie Maker."

This is just crazy - And shows that either he doesn’t know what he is talking about, or he is a micr$oft b*tch regurgitating their propaganda.

See the article of DivX.com forums "WMP vs DivX4.02 Buddy says WMP is better, is he on crack?"

http://www.divx.com/forums/viewtopic.php?topic=19451&forum=5

I have taken time out of my day to prove him wrong, and here is my response to David Johns.

Hi David,

Sorry I couldn't let this DivX vs WMP comparison go... Instead of debating back and forth I decided to make a DivX clip and send it over to you.

When I made this clip, I wanted to use the harshest possible conditions in order to show the true strength of the codec. This is the opening segment of last night's Enterprise Episode.

First, I captured it off of my TV so it’s an analog signal, and I used UYVY format so I only got 16bit colour. As you should know the source is the most important starting step in compression. I assume you are using a digital camera to capture your episodes so I have handicapped myself right from the start. Had I used a digital signal and MJPEG to do the initial raw capture my final production would be even better than what I am giving you.

Second, the opening scenes are quick and fasted paced with little comparison to each other making compression difficult. This means that the file size will be about twice as big as it normally would.

Third, The sound is not just voice but music as well, to keep the quality and stereo settings I used a much higher settings. Increasing the size of the file.

Fourth, You mentioned your final product was around 300kb/s. A close look shows 312kbs, 16kbs of which is your audio. So you video is in fact almost 300kb/s I decided to make my final production less than half that. My video is 93kb/s <That 1/3 your video size> and my audio is 47kb/s for a total of 140kb/s. I could always use your audio codec and make my total file size 1/3 of yours but as I mentioned before I wanted to keep the sound quality. You can check this by first downloading the file, then right clicking on the file and selecting properties and then summary. You will also notice it was saved at 640x480 a much higher resolution than what you are using. Clicking properties while it is streaming doesn't seem to give the bitrate...

That said the file size of this 2:05 clip is 11 megs. a 3 minute clip of this magnitude and difficulty would be around 15meg. However a clip with standard slow action sceens like the ones you are filming would be about half this size. 7-8megs. And if I used mono sound and further audio compression the file size would be even smaller yet.

I watch these episodes on my 36" TV and they are VHS quality or better. So feel free to watch this clip full screen! 640x480 screen resolution will give you the best results. Also, I did not use any filters on this compression. A smoothing filter would again add a bit to the quality.

You will need the 4.02 codec You can get it from here.
http://www.divx.com/features.php

So install it and see what a 94Kb/s DivX clip looks like on full screen. Humor me and I think you will be impressed.

I placed the clip on some web space I have. I don't know how it will stream because my ISP is fairly slow. So if it’s a bit choppy when it streams don't blame the clip, just down load it and view it off your hard drive.

http://plaza.powersurfr.com/mwilliams/divx402clip.avi

I am just a lowly soldier, if you want further details about DivX contact its designers and creators directly.

http://www.divx.com
http://www.divx.com/contact.php ®

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