Saved video file formats

[DWaldie]

Does anyone have a guide to the various video file formats? Some of those listed are pretty obvious but give no real indication of the quality beyond the resolution.

[DVDDoug]

That's a difficult question. There are lots of formats and lots of variations of each format. Some formats are more efficient than others. For example, a 2000kbps MPEG-4 file is half the size of a 4000kbps MPEG-2 file, but the MPEG-4 file might have the same (or better) quality than the MPEG-2.

The best format you are likely to use is high-bitrate*, high-resolution, MPEG-2 for Blu-Ray.

Usually you are limited by your "distribution method." If you are making a regular DVD, it's going to be MPEG-2. Blu-Ray can be MPEG-2 or MPEG-4. If the file is going to be uploaded/downloaded from the Net, it probably needs to be more-compressed than MPEG-2, and you'll need to use more compression (a lower bitrate) than you'd use on a Blu-Ray. If you upload to YouTube, I believe their system will automatically re-encode to their standards so that their player can reliably play it.

Within a given format, a higher bitrate gives you higher quality potential. i.e. If you are compressing a file, a higher bitrate (bigger file) will preserve more of the original quality than a lower bitrate. But of course, simply re-encoding at a higher bitrate or a better format won't automatically improve quality.

Essentially all of the compression methods are lossy. Information is thrown-away during compression. This creates theoritical quality loss, although you don't always notice the loss.

Uncompressed AVI is the least-compressed format at ~65GB per hour (standard definition NTSC or PAL).

AVI/DV (from a MiniDV camera) next with almost the same quality (SD) as uncompressed AVI at ~13GB per hour.

Commercial DVDs are standard definition MPEG-2 typically at around 3GB per hour (depending on the bitrate used). High definiton (high resolution) MPEG-2 requires more space if you want to maintain high-quality .

MPEG-4 and the other "more advanced" formats (DivX, QuickTime, WMV, etc.) can use less than 1GB per hour with standard definition video, but you may not get "DVD quality" unless you use a higher bitrate (bigger file).



* FYI -
Bitrate and file size of any audio/video format are related (approximately) by the following:
File Size in MB = (Bitrate in kbps x Playing Time in minutes) / 140

(You need to include the audio bitrate, and with variable bitrate you need to know the average.)

[DWaldie]

That's a difficult question. There are lots of formats and lots of variations of each format. Some formats are more efficient than others. For example, a 2000kbps MPEG-4 file is half the size of a 4000kbps MPEG-2 file, but the MPEG-4 file might have the same (or better) quality than the MPEG-2.

The best format you are likely to use is high-bitrate*, high-resolution, MPEG-2 for Blu-Ray.

Usually you are limited by your "distribution method." If you are making a regular DVD, it's going to be MPEG-2. Blu-Ray can be MPEG-2 or MPEG-4. If the file is going to be uploaded/downloaded from the Net, it probably needs to be more-compressed than MPEG-2, and you'll need to use more compression (a lower bitrate) than you'd use on a Blu-Ray. If you upload to YouTube, I believe their system will automatically re-encode to their standards so that their player can reliably play it.

Within a given format, a higher bitrate gives you higher quality potential. i.e. If you are compressing a file, a higher bitrate (bigger file) will preserve more of the original quality than a lower bitrate. But of course, simply re-encoding at a higher bitrate or a better format won't automatically improve quality.

Essentially all of the compression methods are lossy. Information is thrown-away during compression. This creates theoritical quality loss, although you don't always notice the loss.

Uncompressed AVI is the least-compressed format at ~65GB per hour (standard definition NTSC or PAL).

AVI/DV (from a MiniDV camera) next with almost the same quality (SD) as uncompressed AVI at ~13GB per hour.

Commercial DVDs are standard definition MPEG-2 typically at around 3GB per hour (depending on the bitrate used). High definiton (high resolution) MPEG-2 requires more space if you want to maintain high-quality .

MPEG-4 and the other "more advanced" formats (DivX, QuickTime, WMV, etc.) can use less than 1GB per hour with standard definition video, but you may not get "DVD quality" unless you use a higher bitrate (bigger file).



* FYI -
Bitrate and file size of any audio/video format are related (approximately) by the following:
File Size in MB = (Bitrate in kbps x Playing Time in minutes) / 140

(You need to include the audio bitrate, and with variable bitrate you need to know the average.)

Many thanks for that. It helps a lot. I understand "i" is interlaced, as in every other display line is shown in each cycle. How does this effect video quality and video size. And what does the "p" signify after the resolution?