it is safe to use Packed Bitstream on Xvid

[afcoff]

I am little bit confused using this option on Xvid. somebody says don't use the Packed Bitstream and other says use Packed Bitstream. I can't understand why they said. enabling this option may effect target size or change the quality of the video. Normally I don't like Low Quality video. I like to encode video High-Qulity. Please tell me this is good or not

[filmboss80]

Test a few short clips at different settings to see what plays best on your player. This is a player related issue. For example, I can play any kind of divx / xvid movie on my PC's media players, but I have a Philips portable unit that chokes on packed bitstreams. So, I encode my vids for optimal playback on that particular unit, and the resulting files play on every other player I own.

[jagabo]

Packed bitstream has no effect on quality and only a tiny effect on file size (on the order of 0.03 percent).

Packed bitstream with 2 (or more) b-frames doesn't play on many older set-top Divx/DVD players. Packed bitstream with 2 b-frames plays on most recent Divx/DVD players. Packed bitstream with 1 b-frame plays on most Divx/DVD players.

[ronnylov]

On my TviX 4000P standalone media player I get better results if I use packed bitstream when encoding xvid with B-frames. Without packed bitstream the player is not playing the videos smootly.

So it depends on your player what type of video it prefers. It is possible to quickly change an already encoded video to packed or unpacked bit stream with a program that I don't remeber the name of...

[dannyboy48888]

Yes and No, Most modern hardware and software players can deal with AVI that are not encompased in a packed bitsteeam. So unless you are having issues dont use it, better yet use MKV or MP4 and definately dont use it

[jagabo]

It is possible to quickly change an already encoded video to packed or unpacked bit stream with a program that I don't remeber the name of...

Mpeg4Modifier

[ronnylov]

Yes, Mpeg4Modifier was the program I usedd to pack/unpack the bitstream of already encoded videos.

[PuzZLeR]

It is possible to quickly change an already encoded video to packed or unpacked bit stream with a program that I don't remeber the name of...

Mpeg4Modifier

Darn. Too late... :P BTW - Very handy program for Xvid/DivX users - saving our butts from bad encodes over the years.

Anyhow, I say don't use packed bitstream unless you know what you're doing. And this compatibility has changed over the years with players. For example, in the past, to optmize packed bitstream you should use only one b-frame. Now, you can use 2 b-frames with some newer players.

The efficiency in a packed bitstream is better decoding and seeking if the player can handle it. I personally say don't use it if you want wide compatibility - the common denominator in playback options is without packed bitstream. The benefits of enabling it are too few in quality and not that worth it for a slightly better seeking. It's player-specific really.

However, having said that, if your particular player plays it (with one and/or two b-frames), and that's all you need it for, and/or you are keeping a copy of the source just in case, and you can undo it anyway, then why not? It's your call.

[jagabo]

The major difference between packed and unpacked bitstream is in editing with VFW based editors. Unpacked is nearly impossible to deal with. VFW is based on a model where it reads one frame of data from the AVI file, decompresses it, then hands the decompressed data to the editor. It can't deal with b (birectionally encoded) frames which require a future frame be decoded before the b frame can be reconstructed.

Packed bitstream was invented to get around this problem. The b frame is packed along with the future p frame into what looks like one frame of video to VFW. A null frame is added to the AVI stream as a placeholder for missing frame. On decoding, VFW reads the packed b-p frame and passes it to the decoder. The decoder decodes both the p frame and the b frame internally. It then returns the b frame to the editor, and keeps a copy of the p frame. Finally, VFW reads the null frame and passes it to the decoder. The decoder ignores the null frame and returns the already decoded p frame to the editor.

In the case of two b frames, both b frames are packed together with the p frame and two null frames are added. Decoding is handled similarly with the full b-b-p sequence uncompressed by the decoder, and the frames returned one by one to the editor.