Thursday, December 20, 2007, 09:00 am
Using iPod & iPhone Video Out: Background and In-Depth Review
45/5G Video iPods
Shortly before the release of the 5G iPod in 2006, Apple designated the iPod Photo as the "iPod (with color display)." The new 5G iPods debuted with the same video output features, but now delivered the capacity for full video playback rather than just photo slideshows.
Between the 4G iPod Photo, 4G iPod (with color display), 5G iPod, and the 2006 5.5G iPod, video playback features remained the same: the four conductor headphone jack supported composite video along with stereo audio, while the Dock Connector supplied both composite and S-Video outputs among its 30 pin package.
The iPhone and 2007 iPods
With the 2007 iPhone, Apple made changes to the headphone jack to support an integrated microphone and call select switch (below). That required removing composite video from the headphone jack, which resulted in moving all video output potential solely to the Dock Connector.
Although not initially advertised, the iPhone also debuted a new higher quality component video output mode which can deliver "Extended Definition" 480i, to deliver the best picture possible when using higher resolution material (the new iPods support playback of 640x480 content or an equivalent resolution in other aspect ratios). Conjecture blogs that weren't aware of this functionality announced that the iPhone didn't have any video output, wouldn't physically work with the older AV Cable, and could therefore never support video output.
After the iPhone was released, Apple launched three new models of video-playing iPods:
- a 6G Classic model that improved upon the existing line of hard drive players.
- a new Nano with video output.
- the new Touch based upon the iPhone.
The iPhone and 2007 iPods were reviewed earlier by AppleInsider, with related notes on their specific video output features:
All of these support the same video output features on the Dock Connector:
- composite video for use with basic TVs
- new component video for TVs that supports higher quality, extended definition widescreen video. Component video provides "YPbPr" signals using three independent channels (luminance, blue - luminance, and red - luminance), and three grounds (one for each signal).
The differences between composite and component video signals are detailed in Inside Apple TV: Video Out to TV.
Classic, Nano vs iPhone, Touch
The 6G Classic and 3G Nano, which are based on a significantly different hardware platform than the iPhone and Touch, also continue to support S-Video output when used with the "iPod Universal Dock" with its S-video connector. The Classic and Nano output an S-Video signal on Dock Connector pins 21 and 22 (counting from right to left when viewing the female connector pins up), use pin 23 for composite video, or alternatively use pins 21-23 for the three component video signals.
The iPhone and Touch don't generate an S-Video signal at all, but use the same pin outputs for composite and component video signals. Apple also notes that the iPhone and Touch generate an 480i (interlaced) component signal rather than the 480p (progressive scan) signal of the Classic and Nano, although I couldn't observe any difference between an iPhone and a Nano playing the same iTunes content to an HDTV.
In order to know which type of video to output, the new iPods have to sense which type of cable or dock is plugged in, and then generate the appropriate signals. All iPods have a sense pin that is used to figure out what accessory or cable is plugged in so it can respond appropriately. Support for existing cables, accessories, and docks depends upon:
- hardware support for the expected signal on the iPod.
- a dock or cable with the physical pins and wires required to deliver the signal.
- an accessory that correctly identifies itself as a suitable output for the signal.
This chart shows the hardware support and cables compatible with each family of video-capable iPods.
The Missing Links
There is one last catch involving the type of dock used. The original iPod Universal Dock routes video signals from the iPod's Dock Connector to its S-Video connector and the video-enabled headphone jack, but does not pass video signals through its own Dock Connector (below). That means it can't be used with either of the new Dock Connector cables. Conversely, the revised Apple Universal Dock only passes video out through its Dock Connector, so it must be used with one of the new Dock Connector cables for video output. Having one set of cables that works with all current and past iPods means fewer boxes to stock and less confusion for users.
To further muddle things however, the iPhone's original Dock Connector does not pass video signals at all. It is visibly lacking conductors for pins 21-23, meaning it can't be used together with either Dock Connector video cable. That means the iPhone must either be used with the new cables directly, or using the optional Apple Universal Dock.
And of course, the iPhone and Touch will not deliver S-Video output even when plugged into the iPod Universal Dock with an S-Video port, because they don't generate an S-Video signal. Further, none of the new 2007 models export any video signal through the headphone jack. That prevents some existing accessories from working with the new models.
Using Video Output
The Classic and Nano iPods offer some video features that are different from the iPhone and Touch. The biggest difference is their photo slideshow mode; on the Classic and Nano, the iPod displays a Keynote-style presenter mode on the small screen (with the current, next, and previous photos to be displayed) and a full screen version of the current photo on the TV (below top and bottom). They can optionally add transitions and music to photo slideshows. When simply looking through pictures, the Classic and Nano don't output a video signal.
In contrast, the iPhone and Touch don't enter a special display mode for displaying photos, and instead just offer to put the photos on TV while you browse them. You can zoom in and out flick between pictures to cycle through your album, but the video output on the TV only presents the standard view, not a live version of the iPhone or Touch screen. Unless you're sharing photos with a group, it may be more enjoyable to view pictures directly from its hands on, zoom and pan interface. Blown up on the screen, photos are larger but not necessarily better looking.
That's particularly the case when using an iPhone or Touch on a widescreen set (below), because photos are not stretched across the full width of the screen as they are with the Nano or Classic iPods, at least not in the current iPhone 1.1.2 firmware. There is a widescreen option pertaining to viewing movies and other video on the iPhone, but no settings related to stretching photos. Wide photos look nicer for landscape pictures, but are less accurate and may also look less flattering in portraits. Video played from the iPhone does present at full width as expected.
In terms of quality, the output of photos on TV is exceptional. This original photo (below top) synced to an iPod Nano and displayed on TV looked good enough for me to capture a zoomed in photo of the screen with a simple camera... and still looks good (below bottom). The difference in the aspect ratio is also highlighted; stretching the picture to fill the screen looks nice but makes the peninsula look miles longer. The iPhone's presentation is more accurate, but the vertical bars on either side could also be distracting.
There is no setup required to use the different cables, because all of the video-capable iPods can sense which cable is plugged in and generate the appropriate signal. This makes using the iPods for video output simple and easy. In comparing the composite and component cables in terms of quality, I couldn't see any real difference at all, even at close range on still photos or frozen video frames. A difference in resolution and signal transmission quality is only really obvious when titles and text are on the screen, and the iPods avoid displaying any hard to read text in their video output.
If you're trying to decide which version to buy, the only meaningful reasons to pick one over the other are the free jacks available on your TV, and whether or not support for previous iPods is important. It appears Apple moved to component connectors largely because that's what new TVs have; many of the new HDTVs only have a single S-Video port or none at all. If you plan to use high quality content such as DVD rips on your iPod using the cables, the component cables could deliver a slight edge, but realistically, there will be no difference to viewers ten feet away from the screen.
On page 3 of 3: iPod Video vs Apple TV; and The Wrap Up
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