First and foremost, the Cowon O2 is made for video playback. Unlike the iPod, Zune, or most video-capable MP3 players, the Cowon O2 doesn't impose many restrictions on what type or what size videos it plays. If your video library is a cornucopia of file formats and resolutions (video podcasts, DivX DVD rips, unprotected DVR files) and you want a zero-fuss way to take that content on the go without the headache of converting files, the O2 is your best choice for less than $300. Specifically, the O2 plays back AVI, WMV, ASF, MP4, MKV, OGM, DAT, MTV, DivX, XviD, MPEG-4, WMV 9/8/7, H.264, M-JPEG, and MPEG 1. The O2 is also agnostic when it comes to video resolution, accepting files all the way up to 1,280x720 at 30fps. It is, however, missing support for MOV, VOB, and the protected WMV format used by Amazon Video On Demand, Cinema Now, and some DVR systems.
Aside from loading, playing, pausing, and skipping around your video files, the O2 also offers advanced features such as manual bookmarking (Cowon calls it "favoriting"), multiple aspect ratios, pan and scan controls for zooming content to full screen, 3D sound enhancement, subtitle support, and the ability to select between multiple audio tracks. Using an optional $10 AV cable, you can also output video (or any of the O2's features) to composite-compatible TV set.
The O2's music features are equally impressive, although, as we mentioned before, sorting through your collection can be a pain. The exhaustive list of format support includes: MP3, WMA, WMA Lossless (not advertised, but it works), AC3, AAC, FLAC, OGG Vorbis, OGG FLAC, Apple Lossless, True Audio, Monkey Audio, MusePack, WavPack, G.726, and PCM. What you don't get is compatibility with DRM-protected WMA tracks (including subscription music) or protected AAC tracks from iTunes. In typical Cowon style, the O2 includes tons of audio enhancement features, including the same EQ presets and BBE enhancement effects found on the Cowon D2 and iAudio 7. The O2 goes one better, however, by including a customizable 10-band EQ with independent frequency bandwidth settings you can switch between narrow and wide.
Video and audio playback are the headline features on the O2, however, Cowon also throws in a voice recorder, text reader, calculator, notepad, and a photo viewer that supports JPEG, PNG, TIFF, and raw images. Because the O2 allows you to both read and copy files from the SD card slot, the player's large screen makes for a handy, portable photo album (or just a nice place to offload photos to free up space on your camera).
The Cowon O2's 480x272 screen resolution is mediocre compared with the breathtaking screens found on the Archos 5 or Cowon A3, but we prefer it to the video experience of the iPod Touch. We noticed some slight darkening on the O2's screen when tilted slightly upward, but viewing angles are otherwise great. Cowon includes display settings for brightness and independent color balance control over red, green, blue, and black. Considering the price, the Cowon O2's video performance is outstanding and the range of playback control and file compatibility is impossible to match. If there's one thing we could change, however, it would be the O2's inability to automatically resume interrupted playback. Sometimes you need to watch a video in small doses, and it's convenient to have a PVP that remembers where you left off. The O2 allows users to manually bookmark their videos, but it's not quite as convenient as the autoresume feature found on the iPod.
The O2's audio playback is fantastic, although the earbuds bundled with the player don't do it justice. All the sound enhancement and EQ features that have made Cowon products such as the D2 and iAudio 7 popular with audio enthusiasts are here on the O2, as well. We were skeptical of the O2's claim to support Apple Lossless music files, but lo and behold, our lossless version of Radiohead's OK Computer sounded beautiful, especially through full-size cans like the Ultrasone HFI-2200.
Cowon claims that the O2 will get up to 8 hours of video playback (under "optimal" conditions) before surrendering. CNET Labs verified Cowon's claims with test results reaching just a hair over 8 hours, putting the O2 far beyond the 4 hours of video life on the Archos 5, and ahead of the 6 hours of video on the iPod Touch. Audio battery life isn't as impressive, rated at 18 hours (CNET Labs results averaged 17 hours), but it's still ahead of the 12 hours of playback time on the Archos 5. Another thing to bear in mind is that all of the O2's competitors require a proprietary cable to recharge the battery, which can be a huge pain if you lose the cable while traveling. The O2 charges best when using the included AC adapter, but you can charge over its Mini-USB connection, as well.