PocketMatrix

OK I did some testing with the Matrix Reloaded teaser trailer. It's the 2.6MB AVI one, 320x144, 1887 frames, 24fps, 1:18 running time, from the main page.

It is showcased in this comparative review:



In that review, I see that my device (iPAQ 3970) should drop no frames playing that trailer.

I did indeed find that I drop no frames playing that trailer on my device, either in the window, or rotated full screen.

I also found that the video quality was not as good as the movies I encoded using the suggested settings in accolon's guide. Is there no way of telling what bitrate was used to encode the video? Which DivX codec?

Let's do some math. Let me know if I am doing this wrong.

According to file info, the audio bitrate is 48Kbps. At 78s, that means audio uses roughly 3744Kb = 468KB. File size is 2648KB which leaves 2180KB for video.

So 2180KB of video over 78s is 27.948KB/s = 223.59kbps.

Is that right? If it is, then this trailer uses comparable video bitrates and better (48 vs. 32) audio bitrates to encode the trailer. Then why does it look worse and play better?

I'm just wondering, could the problem be an issue of file size? It does seem to me that the freezing problem occurs more during the end of the movie, when the player would be accessing the tail end of the large (approaching 200MB) file on my SD card. I can't be certain, but I think it's mostly OK through the beginning and middle of the movie.

Fortunately, this is easily tested. I'm going to take a scene from the end of the movie that is giving me grief, and encode it on its own.

OK, here's the result of my test. The rain scene near the end of A Bug's Life (chapter 33) was giving me grief, freezing with dropped frames.

I encoded it using the same settings (guide settings except 220kbps for video bitrate) as the full movie. The scene plays fine with no dropped frames.

It doesn't look as good quality as the rest of the movie, although it is more of an action scene, and I can't really compare it to before with all the dropped frames. Actually, viewing the scene from my original encoding on the PC, I do see it looks better.

I find that odd considering I used the same settings, as far as I know. Is there an explanation for this? Has the encoding of the entire movie taken bitrate from the beginning of the movie and applied it to the final action scenes? So they look better, but drop frames on my Pocket PC? And the encoding of only that action scene looks worse, but plays better, because it hasn't procured extra bitrate from slower changing scenes? Is that how it works?

[I notice I ask a lot of questions and the only person really answering is myself. I hope everyone is enjoying my dialogue (monologue?).]