Change the MPEG GOP settings.
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MPEG streams are actual saved in multiple Group Of Pictures (GOP) blocks.
A group of pictures contains one I, and several P and B frames. If one looked at the GOP frame sequence, it'd be similar to this "IBBPBBPBBP". Before one changes any of these settings, one should check the MPEG faqs.
-[MPEG Settings]
- GOP Pictures
- The default settings for the GOP I, P, and B pictures are 1, 5, and 2 respectively. The B value is the number of frames to follow the P picture.
For a non-"Closed GOP" the I, P and B picture orders are arbitrary.
Number of I picture(s) in GOP- The number of I picture(s) in the GOP. This is usually set to "1".
Number of P picture(s) in GOP- The number of P picture(s) in the GOP.
Number of B picture(s) in GOP- The number of B picture(s) in the GOP.
Output interval of sequence header- The sequence header holds information on the resolution, aspect ration, and the VBV buffer. This information is used by the decoder upon playback.
This is normally set to "0". In that case, the sequence header is written at the start of the MPEG file. If the settings are changed in the [Force Picture Type Setting] window, this should be set to "1".
Max number of frames in GOP- Set the maximum number of frames per group of pictures. This governs how often to insert an "I" picture. This needs to be set if "3:2 Pull-down" or "Inverse 3:2 Pull-down" is selected for the "encode mode" in the [Video] tab.
Normally, this is set to "0", which does not limit the size.
DVD video uses this. For example a NTSC DVD is restricted to a maximum of 36 frames, so one could use 18 without any trouble.
"Closed GOP"- Enable this if one is planning to reedit the file with other software. This option removes data dependencies between GOPs.
Checking this option removes the "B" picture dependencies from the GOP which causes and increase in file size.
Detect scene change.- Enabling this can help detect scene changes and thereby decrease degradation between scenes caused by compression.
The the color characteristics between I pictures, scene changes can be detected. Since the encoding relies on temporal information, it's best to enable this.
This can not be used concurrently with "Force Picture Type Setting".
"Force Picture Type Setting" and "Settings" Button- The [Force Picture Type Setting] window's settings can be used to brute force GOP frame content and locations. Check this box to use those settings.
One doesn't need to check this if one does not want to use special GOP structure formats. Don't forget to set up how to manipulate the GOP via the "Settings" button.
-[Force Picture Type Setting]
"I Picture Only" Button- Construct the GOP from the "I" picture only. This will result in horrible encoder efficiency. Use this only if one is planning to reedit the file.
"I, P Picture Only" Button- Construct the GOP without the "B" picture. This will produce a high quality picture for scene with motion, but greatly increase file size.
"Standard" Button- Use the standard TMPGEnc GOP.
"OK" Button- Close the window and save the new settings.
"Cancel" Button- Close the window and discard any changes.