to select your mpeg-2 ibp settings:1 click the configure button if you??re performing a realtime export to disk, or click the format button if you??re defining capture settings. this displays the following dialog box:
2 to automatically set dvd-compliant settings suitable for use with dvd authoring programs, click the default button. for example, if you??ll be exporting video for use with dvdit! le, your material must be dvd-compliant.
if you want to specify a custom configuration, such as by changing the bit rate type or gop structure, make sure that your settings are supported by the program you??ll be using with your .m2v file. changing the gop structure may give you undesired results. you should change these settings only if you??re an advanced user.
3 under data rate settings, select one of the following bit rate types:
- constant bit rate (cbr) video is compressed at exactly the data rate you select. this is useful when you need to limit or predict the size of your .m2v file. however, if your video is very complex (such as scenes with lots of movement or many colors), you??ll need to select a high data rate to avoid having frames of very blocky video in your .m2v file.
- variable bit rate (vbr) video is compressed at varying data rates based on the complexity of the video. the data rate you select is used as the average target data rate for the compression.
4 drag the data rate slider until your desired data rate is displayed. the higher the data rate you select, the better the video quality will be.↑1
the maximum recommended dvd-compliant data rate is 7.0 mbits/sec (0.83 mbytes/sec), which should give you good results with most dvd authoring programs. if you select a higher data rate, be aware that it may not be supported by your authoring program. for charts of recommended data rates, see "recommended mpeg data rates for distribution on dvd-r or cd-r" on page 227.
5 you can customize the gop structure of the mpeg-2 compression as follows:
- gop length determines the number of frames in the gop (group of pictures).
- subgroup length determines the subgroup length of b-frames and/or p-frames in the gop, after the initial i-frame. a subgroup of 3 appears as "bbp," a subgroup of 2 appears as "bp," and a subgroup of 1 gives you only p-frames after the initial i-frame.
6 click ok to save your settings.
1 when selecting the data rate for a matrox codec, be aware that a megabit (mb) is equal to 1,000,000 (1000 × 1000) bits, and a megabyte (mb) after binary conversion is equal to 1,048,576 (1024 × 1024) bytes.