videobear
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Mar 31, 2006, 9:41 AM
Post #5 of 6
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Re: [achilles23] Video Quality
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Spot's right about bitrate. A higher bitrate means better quality in image or sound. Lower bitrates mean lower quality, but you can fit more material on a disc. Your files can be encoded using either constant or variable bitrate (CBR or VBR). If you use a constant bitrate, you know how much video you can fit on your DVD, and you know what the quality will be. If you use VBR, the encoder will use a lower bitrate for scenes that won't be affected by doing so, and a higher bitrate (up to the maximum you specify) for scenes that need it to preserve their quality. By doing this, you can get a result with a higher perceived quality to fit into a smaller space than you could with CBR.
AC3 is a digital audio format developed by Dolby. It's often used when encoding surround sound, but it's also the "standard" audio format used for DVDs. When using AC3, you create a separate audio file from your video file. I don't know if iDVD can handle AC3.
PCM stands for "pulse code modulation", but that's not the important thing about it. It's the "other" digital audio format for DVDs. When using PCM audio, your video and audio are lumped into the same MPEG2 digital file. PCM audio takes up more "room" than AC3, so using it means that you can get slightly less video onto a DVD.
Regards,
Doug Graham
Panda Productions
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