WMV to DivX ,but what video rate for TV???

[neo76]

Hi,

I'm using Xilisoft to convert some WMV files to DivX format so that I can play those files on my standalone dvd(that plays Divx) player. Now I haven't purchased the dvd player as yet but i'm in the process of converting the files.

Theres no problem with conversion, the only doubt i have is what is the ideal video rate i.e. 352X240 or 640X480 etc, that I need to enter so that the DivX file looks good on my TV. Before i convert with a particular rate and find out that it doesnt look good or its blurred I would like to know the exact rate that looks normal on my 21" TV.

Thanks,
Neo

[neo76]

By the way, the input rate for all the wmv files are mostly 352X240. there are some with 640X480 too.

Thaks,
Neo

[jagabo]

Generally you want to encode with the same frame size as your source. Using a smaller frame will lose detail. Using a larger frame will just give the encoder more data to compress. You can't create detail that isn't in your source.

You may need resize to adjust the aspect ratio. Many Divx/DVD players assume square pixels in MPEG4 files. So a 352x240 (most likely a 4:3 display aspect ratio) may look a little wide on TV. Resize to 320x240 or 352x264.

Another case where you need to resize is when the frame size is bigger than 720x480 or 720x576. Most players will not play files with frame sizes larger than that so you have to reduce them.

[neo76]

Thanks jogabo. My point is will a 320X240 frame size video look small or fit the entire screen on a 21" TV? Or do I encode it at 640X480 so that it fits my TV screen size?

The input frame for most of the clips are in 320X240 format.

Thnx,
Neo

[edDV]

Thanks jogabo. My point is will a 320X240 frame size video look small or fit the entire screen on a 21" TV? Or do I encode it at 640X480 so that it fits my TV screen size?

The input frame for most of the clips are in 320X240 format.

Thnx,
Neo

The DVD player (with divx decode) does the scaling to the analog TV outputs. Both will fill the screen. 640x480 will show somewhat finer analog detail that 320x240. The better your TV the more you will see the difference.

In a similar way, the computer graphics card (RAMDAC to NTSC/PAL analog outputs) does the same from a software divx player.

[neomaine]

neo76,

Your original frame size (its NOT video rate) is just fine at the VCD or 1/4 DVD resolution of 352x240. I would change nothing. It will scale to fit the screen proportionally...which is what I believe you're looking for and what matters. The 'video rate' should be 29.97fps for smooth motion. Though I don't work with xvid/divx but the same principles should work fine.

Now if your worried about blurriness then the 'video' rate you're referring to is actually the bit rate. Something you should see in the properties of your original file. It determines how much information is contained in each frame. Generally, the more bit rate the closer to the original the new video will be. There is a certain point of diminishing return. From what I've read a bit rate of 600k to 800k should be plenty for the divx/xvid codec to minimize compression artifacts with the resolution you've mentioned.

I'll let others more knowledgeable with divx/xvid and familiar with using a resolution of 352x240 to say whether or not the 600-800k bit rate will work. Its just a guestimate on my part.

[neo76]

Thanks a lot Neomaine. Will convert at original frame size and let you know how it looks.

Neo

[jagabo]

If you don't need your files to be a certain size you can set Xvid to perform a constant quantizer (constant quality) encoding. Just pick the quality you want and encode with a single pass. It will use exactly the bitrate required to get the quality you asked for.

With the quantizer set to 2 the compressed file will look almost exactly like the source. At 3 there will be a little macroblocking if you look at enlarged still frames but you won't notice it at normal playback speeds. As the quantizer value gets higher the file will get smaller but the quality will decrease.

Try setting the quantizer at 3 or 4 and see what you think of the results. To save time you can encode short segments for testing purposes.