B-frames and Trellis quantization?

[RioCreations]

I have read the How To section of the Website and I'm beginning to understand ffmpegX but I still don't understand what B-frames and Trellis quantization mean or what they are used for. They are in the Options Tab under mencoder XviD options. Can anyone help me please?

Rio.

[jpschuck]

I have read the How To section of the Website and I'm beginning to understand ffmpegX but I still don't understand what B-frames and Trellis quantization mean or what they are used for. They are in the Options Tab under mencoder XviD options. Can anyone help me please?

Rio.

B-Frame is a specific type of frame. Usually when using video temporal compression each frame is defined according to a series of modifications applied to the previous frame ; i.e : frame 2 is the same as frame 1 except for a number of additional details.
When using B-Fame, it can also be defined according to next frame, i.e. frame 2 is the same as frame 3, minus a number of details.
Of course the video decoder has to be aware which picture is referred to and must first decode frame 3 in order to decode frame 2. That's why a given hardware has to be B-Frame compatible in order to be able to decode a video using B-Frame.
The advantage of the B-Frames is that they require less disk space, and allow smaller bitrate/filesize for a given quality.

Trellis quantization is used in order to optimize motion estimation. It also allows smaller bitrate for a given quality (but slows down encoding time). As far as I know, Trellis Quantization is just a better method of analysis so there is no impact on the output file's compatibility.

[RioCreations]

Hi jpschuck,

Wow! Now that's what I call service and a well written explanation! I thank you very much for taking the time to answer my question. I could need some more help if you don't mind?

I have a japanese animation in an .avi container from the web. I want to convert it into AVI XviD and then burn it using iDVD to watch on a standalone DVD player. I'm don't have lots of technical knowledge...Do I need to apply B-frames and/or Trellis quantization to achieve the best possible quality? The original .avi file is 700MB.

And also, if the original video file's framerate is 23.976 fps (NTSC FILM), do I need to leave it the way it is or should I change it to NTSC (29.97 fps)? I live in Canada and I think the original comes from Europe.

Your help is greatly appreciated.

Rio.

[jpschuck]

Hi jpschuck,I have a japanese animation in an .avi container from the web. I want to convert it into AVI XviD and then burn it using iDVD to watch on a standalone DVD player.

First of all, if your movie is already in an .avi container, why would you convert to XVID in the first place ? Isn't it already an XVID/DIVX movie ?
As far as I know iDVD handles any Quicktime readable file. All you need is the correct Quicktime Component (a.k.a Quicktime Codec) so iDVD can convert your .avi file to standard DVD format (MPEG-2).
Official DivX component for instance, if your movie is using divx/xvid.

I don't have lots of technical knowledge...Do I need to apply B-frames and/or Trellis quantization to achieve the best possible quality?

Yes, _generally speaking_ it's better to use B-Frames and Trellis Quantization to achieve the best possible quality when encoding to XVID/DIVX. But keep in mind that some hardware DIVX player are unable to read B-Frames.

And also, if the original video file's framerate is 23.976 fps (NTSC FILM), do I need to leave it the way it is or should I change it to NTSC (29.97 fps)? I live in Canada and I think the original comes from Europe.

I suppose should always avoid unecessary framerate changes, so if your movie comes in NTSC Film, try to keep it that way. I'm not sure though (is it evn possible within iDVD ?), because I live in France and we're using PAL (25 FPS) instead of NTSC.

[RioCreations]

Hi jpschuck,

I had originally converted the .avi video file into DVD format and it had authored as VIDEO-TS but there was no sound when I played it on my old Panasonic standalone DVD player. I also wanted to cut the movie into 5 min chaters but could not find that options in ffmpegX. Then I tried some other japanese animes that are in .ogm files and converted them into AVI XviDs which I imported into iDVD and then cut them into 5 min chapters and burnt the DVD. It worked fine and the audio .mp3 was fine. That's why I tended to stick with the AVI XviD format and the .MP3 sound choice.

Although I'm limited to a maximum playing time of 2hrs in iDVD, it doesn't bother me that much since by adding Menus, Sub-Menus and backround pictures, it dresses everything out nicely and fill up the rest of the DVD.

I even boosted up the image size in the Video Tab in ffmpegX by fear of having a fuzy picture on my TV set once converted because the original size only has 700MB. I'm not sure if boosting the image size matters much but I wanted the best quality possible.

Maybe you could help me with another matter with ffmpegX:

Here is how I first installed ffmpegX 0.0.9u (I could not get version x r2 working):
1) I created a Folder on my desktop containing the main App and the 3 binary components.
2) I copied the ffmpegX main Icon to my Applications Folder.
3) I opened the ffmpegX from the Applications Folder.
4) It asked me to locate the 3 binary components (which I did) and then I type in my Mac's password for ffmpegX to install the components itself.
5) ffmpegX installs the components (it creates an ffmpeg Folder in HD\Library\Application support\ffmpeg.
6) The ffmpegX App opens and it is ready to go...but...

However, the App did not recognize all my video files (AVI, OGM and MKV).
I then started my 6 steps from scratch after uninstalling ffmpegX and its components.
The only thing I changed is that now I run ffmpegX 0.0.9u from my dekstop from within a Folder I created onto my Desktop. I did not copy the main ffmpegX Icon to My Applications Folder this time. Now everything works like a charm! The only thing that is annoying about this method is that every time I open ffmpegX 0.0.9u by double clicking the .dmg icon and then its Icon, it asks me to relocate mpeg2enc and type in my password again...but it works!

What would be YOUR opinion in running ffmpegX 0.0.9u or ffmpegX 0.0.9x r2 from my Applications Folder correctly, I'm open to suggestions. I have no special characters or spaces in my Folder names.

Rio.

[jpschuck]

I then started my 6 steps from scratch after uninstalling ffmpegX and its components.
The only thing I changed is that now I run ffmpegX 0.0.9u from my dekstop from within a Folder I created onto my Desktop. I did not copy the main ffmpegX Icon to My Applications Folder this time. Now everything works like a charm! The only thing that is annoying about this method is that every time I open ffmpegX 0.0.9u by double clicking the .dmg icon and then its Icon, it asks me to relocate mpeg2enc and type in my password again...

This is a bit confusing. Do you mean that each time you're starting ffmpegX from within the .dmg file ?

What would be YOUR opinion in running ffmpegX 0.0.9u or ffmpegX 0.0.9x r2 from my Applications Folder correctly, I'm open to suggestions. I have no special characters or spaces in my Folder names.

Are you sure your Applications folder has the correct permission settings (system->read/write ; admin->read/write ; others->read only) ? Is your account an admin one ?

When you say "the App did not recognize all my video files (AVI, OGM and MKV)", do you mean that "no video files are recognized" or "some files are not recognized" ? By the way, what do you mean by "not recognized" (error message...) ?

[RioCreations]

Hi jpschuck

Sorry it took a little while for my reply...Yes, I run ffmpegX 0.0.9u from the .dmg everytime I use it. When I tried to run it from within the Applications Folder and I opened an .avi, .ogm or .mkv file into it, it would indicate UNRECOGNIZED in the source window of the Summary Tab. It indicated No files in the video and No Files in the audio source. Then after I trashed the App from the Apps Folder and its its Binaries from within the Application support Folder, I tried running it from my Desktop and then it recognized all my video files. I left it that way but it still asks me to locate mpeg2enc.intel each time I open it. I wish I could have gotten version 0.0.9x r2 working that way but it still indicated UNRECOGNIZED in the Source of the Summary Tab. That's why I stayed with 0.0.9u for now. Weird! I'm the only user on my computer and I have no spaces in my HD name.

I even boosted up the image size in the Video Tab in ffmpegX by fear of having a fuzy picture on my TV set once converted because the original size only has only 700MB and I wanted it to fill a 4.7GB DVD disc. I'm not sure if boosting the image size matters much but I wanted the best quality possible. What's YOUR opinion on my situation?

Rio.