Twelve Black Code Monkeys

Since writing my last entry, I hadn’t done too much with video on my iPod other than download a few video podcasts. However, this last week I decided to put an episode of West Wing on the iPod. West Wing is actually in widescreen format. I encoded it with a 640×360 resolution accordingly and this produced what I thought was a flawless program. No banding even the resolution was higher than that of the iPod screen. This made some sense because the banding that I noticed for the full-frame clip I was using for my testing was mainly in the top 10th of the screen.

(Note: after writing this article, I’ve done much more research on putting videos on an iPod and wrote up a new article that covers this in more basic terms - A Beginner’s Guide to Video for the IPod. I urge you to read that article first, especially if you don’t have much or any experience with digital video, the iPod, or both together)

Great, I thought! Now I can at least use one format for displaying on the iPod or the TV. But wait, it gets better!

I decided to copy an episode of Six Feet Under onto the iPod and test out another hypothesis by the moderator of the Videora iPod Converter forum, Sketchy, that you should make sure that your resolution was divisible by 16, since MPEG4 divides the screen up into 16×16 blocks. 640 and 360 are both divisible by 16[it turns out 360 is not divisible by 16, oops, but read on], so maybe that was the key to flawless, higher-resolution video on the iPod. The previous 544 x 408 resolution wasn’t [and it turns out that it wasn't even the highest resolution allowable - it's 552 x 414]. 544 is divisible, but 408 isn’t. In order to maintain the 1:33 aspect ratio, the highest resolution you can use that doesn’t go over the total pixel count of 230,400, but which is still divisible by 16 in both width and height, is 512 x 384[oops again, it turns out that it is 528x400] So, I encoded the program using this and voila, perfect-looking video!

Great news again, right? Now I can do the same thing with full-frame videos and just use that one resolution for both iPod viewing and TV viewing. Sure 512 x 384 isn’t HD, or even DVD quality. But it’s perfectly watchable on even my 34″ TV. Yet again, though, it gets better, or perhaps better and worse at the same time?

I thought I should update the spreadsheet with this information, so I dug out the old 55-second clip, and proceeded to convert it again but this time using the new 512 x 384 resolution instead of the older 544 x 408. I did this for all the various modes, 1-pass and 2-pass, and put them on the iPod. I started watching them and they all looked great! This wasn’t a big surprise, since the Six Feet Under episode also looked great. But here is the weird part – I also reloaded the old 544 x 408 clips for comparison sake and when I started watching some of these, they also looked absolutely fine! No banding whatsoever! I was flummoxed.

So I bring my iPod into the bedroom where my wife is still half awake and ask her to look at these since I’m starting to not trust my own eyes anymore. Only when I play them for her, the banding is back! And it’s not just back on the old clips, but the new clips as well. Huh? When I was first playing them back in the office, my iPod was plugged into the computer getting charged, so I thought, hey, maybe that has something to do with it. So I plug it into the wall and try again. No go, the banding is still there. I than decided to try one more thing – I reset the iPod. Once I did this, no more banding was visible!

So, to conclude, the problems with banding are not unavoidable. If you experience them, just reset your iPod. My guess is that putting the iPod in and out of video mode can produce this artifact, but if you just watch one program straight through, there shouldn’t be an issue. Of course resetting can be a nuisance, but if you were interested in only storing one format for a given file which you plan to view on both the iPod and a TV (or your computer), then it might not be that big a deal.

Based on this further development, I’ve edited the spreadsheet and included the new information. Based on this new information, my conclusion is a bit different. Basically, if you never see the possibility of wanting to play these files on a TV or computer, then you should stick with one of the 320×240 resolutions, preferably one that has a higher bit rate that would produce less artifacting. As I said above, H.264 > CBR, 1 pass is a good option since it’s fast to convert and small in size. This will allow you to convert an hour’s worth of video in a little over an hour and will produce a file that is about 380MB.

However, if you do want to have a single file for multiple uses – iPod viewing, TV viewing, computer viewing, then choose one of the 544 x 408 552 x 414 resolution ones, again with the higher bit rate (or lower Qscale). I’ve found I can’t really tell the difference between the higher bit rate (lower Qscale) versions. They all look incredibly crisp and clear, with no artifacting. However, the one that seems to come out on top in terms of both a smaller size file as well as a faster conversion is the plain MPEG4>CBR yet again. For a one-hour piece of video, the conversion time will likely be between two and three hours, perhaps closer to three. The file size will be about 1GB. That’s not really much better than the video stored on a DVD, which is definitely better quality.

Obviously the tradeoff of having the flexibility of one file for all purposes is that it will take a lot longer to convert your video and it will also take up considerably more space – maybe three times as much! For some people, though, this is a good compromise. For others who want to store more on their iPod but still want the possibility of displaying their videos on a TV via the iPod, yet another option might be worth the additional time – actually encoding it in both a 320×240 version specifically for viewing on the iPod’s screen, and an additional version at 544 x 408 552 x 414. This latter version could be archived on your hard drive or even DVD-R, although at 1GB/hour, you might need a lot of DVD’s to store a big collection!

Personally, I don’t have the time, patience or storage space to convert my DVD collection, so I suppose I will just convert things as I feel the urge to watch them and will probably use the higher resolution unless I have no intention of watching a given video via the TV…

There are many programs currently available that will convert video of various kinds to a format compatible with the video iPod. While none of these are prohibitive in cost, I didn’t feel like spending lots of time downloading trial versions to figure out which one might work best, nor did I feel like spending on one that a few people like only to discover there’s another that actually does a better job. Since the video iPod is so new, many software companies that make converters are just now modifying their products to include conversion options for the iPod. Maybe in a month or two the dust will have settled a little more and we’ll start seeing some in-depth reviews comparing some of these applications to one another.

(Note: after writing this article, I’ve done much more research on putting videos on an iPod and wrote up a new article that covers this in more basic terms - A Beginner’s Guide to Video for the IPod. I urge you to read that article first, especially if you don’t have much or any experience with digital video, the iPod, or both together)

In the mean time, as far as I’m aware, the only free program that’s been available is one from the same people who brought you PSP Video 9 (a video converter for the PSP) and Videora. The name of the program is “Videora iPod Converter” and it has a wide (and sometimes overwhelming for a newbie) assortment of settings one can manipulate for your conversions. Aside from the obvious ones like resolution and bit rate, there are others like Qscale, and conversion mode that are not nearly as well known.

As with much freeware, there’s no real documentation available, nor is the program very straightforward to use. You need to create a profile for a given collection of settings, or use one of the programs presets. If you choose to use your own settings, you’re in no way guaranteed that they will work with the iPod. You may be able to get them into iTunes but they won’t transfer to the iPod if some setting is off.

A Quick Note: I’ve done some additional testing and posted some updates to this entry, so if you’ve found it via Google, please see my Converting Videos for iPod, Take 2 entry after you’ve read this one.

Screenshot of Videora iPod Converter converting a file

Screenshot of Videora iPod Converter Profile Screen

The two settings that this happens for most often is bitrate and resolution. The iPod will only handle resolutions that add up to 230,400 pixels - whatever the width and height dimensions are, multiplied they can’t add up to more than this number or the file won’t transfer. Similarly, for H.264 files, iTunes will not transfer it if it has a higher bit rate than 768Kbps – although at least in this latter case there is a hack to get around this, thanks to a user on the Videor iPod Converter board named DaProphecy. Apparently the chip in the iPod that plays video has the ability to play higher quality video than Apple lets on in their specifications. iTunes prevents you from transferring in this higher bitrate despite it being playable, so you basically have to trick iTunes into transferring the file. This, of course, is ridiculous and should not require a hack to get around. Hopefully Apple will update iTunes and make this a non-issue.

Because of the massive numbers of settings, and no real clue as to which ones would work best in which cases, I determined to spend an inordinate amount of time transcoding a 55-second video clip into as many of these as made sense at the time. In all, I made 40 different conversions, although I’m sure I barely scratched the surface in terms of what I could have done. Still, I wanted to get a general sense of what each setting would do, how they would compare to each other in terms of the amount of time the conversion took, how big the file was, and what the quality of the video was both on the iPod and when exported out to a TV. I figured if I was going to convert my 200+ DVD library to video files for the iPod, that I should be fairly certain what settings to pick so that I don’t waste time converting to something which in the end wasn’t as efficient as another format in terms of time and storage space.

I set about creating an Excel spreadsheet, linked here, which contains all my data, as well as my impressions of quality. The first sheet shows various conversions to H.264, whereas the second sheet displays results for conversions to MPEG4. Both of these are compatible with the iPod.

To summarize my findings, much of it was predictable. Usually the higher the bit rate, the better the quality, although occasionally it was hard to tell the difference. When exported to TV, the higher the resolution, the sharper the image. However, there were some findings that I hadn’t expected. First of all, making a 2-pass conversion usually did not improve the video noticeably, but did double the time needed to convert. File sizes for 2-pass conversions were almost always about the same give or take, the only big exception being MPEG4 > QC-VBR mode, which decreased the file size by about 2/3, although unfortunately this smaller file size also equated with much poorer quality video.

While I probably will not use it extensively, the iPod’s ability to pipe the audio and video out to a TV is something that really interested me. While critics complain about the size of the iPod’s screen for video, you can’t complain about it if you pipe that video out a 27” (or greater) monitor. I own a 34” widescreen TV which I suppose is about the same as a 27” standard (4:3) TV and used that for testing these conversions (as well as viewing them on the iPod itself). One thing I found interesting was that some video artifacts were much more noticeable on the iPod than on the TV– for example some pixilation when clashing colors like red and green were adjacent to each other. Even some of the “blotchiness” of certain colors seemed less noticeable sometimes on that large screen. I was viewing it from about 5 feet away, which I think is equivalent to holding the iPod about 5 inches from my face! I expected all the defects to be much more obvious, but perhaps the interlacing of a TV screen somehow smoothes out some of these.

What I did find was that some of the higher resolution conversions I made, when played on my TV, were excellent in quality. Perhaps not quite DVD quality, but maybe equivalent to a VHS tape if not even cable or even satellite. Unfortunately, these same files, when played on the iPod, had artifacts that made them difficult to watch – similar to the “banding” that one might get and worn VHS tape. This was particularly evident whenever the camera panned at all. So my initial hope that I’d be able to convert one file and have it play in optimal quality on both the iPod as well as the TV was not to be. The lower resolution conversions are not terrible when viewed on the TV, but it’s pretty obvious that something’s off, at least from 5 feet away. The picture just isn’t very sharp, even with the best conversions. It’s a little like watching a 30-year-old TV.

As far as the conversions themselves go, they took a bit longer than I expected. Even the shortest one took about 15% more time than the clip itself, and the worst took 700% as long! Then again, you may have different results. I converted these on a 2.5-year-old laptop with a 2Ghz P4 processor and 1.25GB of RAM. Very possibly you have something newer and faster. File sizes varied greatly as well, from a small 3.4MB to a whopping 25.6MB for just this small clip. Luckily, the 2^nd Pass, which normally doubled the time to convert, was usually not a factor in terms of quality. And file sizes didn’t always equate with quality either.

This photo was taken from my TV. It was a lower bitrate setting and you can see blotchiness, pixelation, and other artifacts pretty clearly.

Here’s another picture off of my TV, but this one at a much higher bitrate. While still not crystal clear, it definitely looks much better than the first image!

I have to divide my conclusion into to separate categories – best for iPod and best for iPod to TV. If one is mainly concerned with playing on the iPod itself, it seems the winner is probably H.264 > CBR at 768Kbps, 1 Pass. This has one of the smallest file sizes and fastest conversion times. It’s certainly possible that some may find some of the other modes to edge it out slightly, but most of those modes produce files that are at least double the size, maybe more, and take at least a little more time to convert. But if storage isn’t an issue (on the iPod itself, even at the higher 60GB level it still IS an issue), and your system is incredibly fast, or you have extra machines to do conversions for you, you may find it more worth it to try some of the other settings.

For iPod to TV, the winner seems to be MPEG4 > CBR at 544×408, 2500Kbps and one pass. This had one of the shortest conversion times and the smallest file size for a higher-resolution conversion, and rivaled or beat all of the other such conversions.

A final disclaimer: these quality settings are of course subjective. As they say, your mileage may vary. I’ve compared a pretty limited range of video information in a 55-second clip, and I’ve done this for each of the 40 files on both the iPod and the TV. That’s a lot of stuff to compare even for a relatively short clip. I’ve already spent a week or so transcoding and then reviewing all of these, but I can see where to really scrutinize this stuff in detail, one would need a larger clip with a lot more variations in color, motion, etc., and have the luxury of being able to review each clip about 20 times to note various things down. I’m not even an expert at any of this and so my impressions are from someone who is not a videophile per se, but just a gadget freak who also loves to watch DVD’s. So please take this all with a grain of salt. I did the best estimation I could within my limited timeframe, expertise, and tools, but I can’t claim this as being at all definitive. I look forward, in fact, to those who might be able to clarify, confirm, or dispute certain findings so that a more accurate picture for all can be obtained. In the mean time, I hope this serves as a decent primer for those who, like myself, found themselves lost in the sea of possible settings with no idea how they might translate into quality, time, and space in the real world.

Update (12/23/05): It turns out this is far from the end of the story. I’ve discovered some new peculiarities with video for the iPod that caused me to write a whole new blog entry, so if you’ve found this article via a google search or a link on a discussion forum, etc., you might want to check out my newest entry, Converting Videos for iPod, Take 2.