[General Topics] Menneisyys:
1.4.7 Resolution-dependent benchmarks

I’ve also made some resolution-dependent benchmarks to see how the players behave with non-QVGA / VGA source videos. In this test, I’ve let Nero Recode set the target resolution depending on the manually set bitrate.

Incidentally, this (Nero Recode itself decides the best resolution for a given bitrate) is the default how encoding works. This may be an overkill in a lot of cases. For example, even a 200 kbps 640*272 AVC stream looks great, while Nero Recode insists of only allowing for this size at the bitrate of 533 kbps. This is a big overkill if your premium concern is storage space. Again and again, even 200 kbps 640-wide streams can look great, particularly those of “traditional” “35 mm” (2:39:1) movies. No need for wasting almost three times more storage on the video stream.

Therefore, if you do want to ALWAYS force the Nero Recode to convert your videos / DVD’s to either 320- or 640-wide videos, you must manually click the Video button (the lowermost large button on the right), go to the Resize tab and fill in both the horizontal and vertical size. In THIS screenshot, I’ve filled in 640 for the horizontal and 272 the vertical size. Uncheck the “Letterboxing” checkbox (if ticked).

Note that, as there’s no “keep aspect ratio” functionality in here, you must manually compute the vertical size, based on the original one. That is, if the original is, say, 720*300, then, you’ll need to

1, divide 300 (the original size) by the result of 720/640 = 1.125 (or, if you plan to watch the video on a QVGA screen, 720/320 = 2.25). The result is 266 (or, with the QVGA case, 133).

2, now, you’ll need to find the least multiple of 16 closest to the result. To find it, divide 266 (133) by 16 and round up. The results are:

266 / 16 = 16.625; rounded up: 17

133 / 16 = 8.3125; rounded up: 9

3, multiply the rounded-up integer with 16 (272 and 144, respectively); this will be the new vertical size.

Now, the chart:

With exactly the same video files (and, in addition, with a one pass, one soundtrack, no subtitle file and a iPod 5.5G –specific one to see whether they result in a better performance), I’ve also made some other tests with the three VGA devices to see how they play them back. As can clearly be seen, there isn’t much difference.

First, the results clearly show including a second soundtrack and/or subtitles doesn’t really cause any real speed hit. That is, feel free to do it if you’re either a language buff (and like watching movies in different languages) or would like to listen to the commentary soundtrack, if any. (Note that, currently, few desktop-based media players can display the Nero subtitle streams: of course, Nero’s own Showtime and VideoLAN.)

As can also be clearly seen (just compare the 640-wide result to that of the 624 and the 688-wide: as can clearly be seen, there isn’t much difference), the overhead caused by having to resize the video to (horizontally) fill in the entire screen is pretty low (as opposed to what some people state).

Still, as you won’t take advantage of the extra 80 pixels of the original 720-wide video, there isn’t much point in NOT reconverting it. Again and again, with AVC videos and current hardware (that is, before the VGA iPAQ 2xx series with the Marvel Xscale CPU’s hits the street and CorePlayer receives support for it), you MUST convert your videos to be enjoyable on your handsets – as opposed to most ASP videos played on most Windows Mobile / hi-end Symbian handsets.

The other direction (not using a full 640-wide stream), on the other hand, can pay off. If you don’t want to disable any of the special AVC features (deblocking / CABAC / Bidirectional Prediction), then, resizing your videos to be 544 pixels wide will still yield an above-100 benchmark, meaning flawless playback (mostly) without dropped frames.

There is another usage area where you can make good use of the almost non-existing performance degradation caused by CorePlayer’s reisizing the non-320/640-pixels-wide content to the screen. For example, take the example of the QVGA Nokia N95, which has an analogue TV output. A 320 pixels wide video is pretty much pixelizated; a 400-pixel-wide isn’t so. The latter is still on the verge of playability without (many) dropped frames (and, if you’re lucky enough, even without having to disable deblocking). Therefore, in cases like this, it’s preferable to create a 400-pixels wide video, which can be played back pretty well on both the built-in QVGA (320 pixels wide) screen and an external TV set. (Also see THIS for more info on this subject.)