Posted: Fri 7 May 2004, 4:40 Post subject: encode mode explanation please
I am confused. Here is situation. I have a DVB 544x480 mpeg 2 I want to convert to 720x480 DVD format using TMPGEnc. Should I encode non-interlaced or interlaced. On playback i see picture quality is higher on non-interlaced encode method as opposed to interlaced option. Also on GOP settings, should I choose standard or I,P only. Main tutorial doesn't offer any explanations other than authors preferences. Please advise.
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Fri 7 May 2004, 15:16 Post subject:
The GOP structure has nothing to do with interlacing or resolution. The most appropriate picture types depend on how high your bitrate is and how much motion your scene has.
B pictures give the best relationship between quality and compression, but never give top quality. Use them only if your average bitrate is low.
If you have enough space to use a higher average bitrate (ex., 6500 or more), you can stick to using I and P pictures only (ex., IPPPPPPPPP\). Generally, long GOPs (10-15 frames) will give you better quality, because the bits that are saved on the P pictures can be used to improve the I pictures (which in turn improves the whole GOP). If your video clip has very fast motion, you may get better results by reducing the size of each GOP (ex., IPPPP\). It's really not an exact science; you need to test it for each type of footage.
As to the interlacing, it depedns. If your source movie runs at 24 fps, you can create a non-interlaced DVD with the pulldown flag activated (your DVD player will then interlace it during playback). If your source is 29.97 or 25 FPS, the resulting DVD needs to be interlaced (or it won't be compatible with many players). However, make sure you set the "video source type" to non-interlaced.
Stretching the image from 544 to 720 pixels is going to cause some loss of quality, but at least your source has the right number of lines, so it should still look pretty good.
Make sure you check the results on a video monitor or TV set. PC monitors do not play interlaced video properly.
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