BD-Rebuilder: Understanding iPad resolutions

[Stormcrow]

Hi,all.

I'd like to re-encode some 16:9 1080p BD movies to alternate-output iPad HD. I don't have an iPad in my hands yet, so I can't experiment. I need to pre-prepare some content.

I'm trying to understand the implications of the 2 iPad HD options.

The iPad has a 1024 x 768 display.

- I can either re-encode to fit the max 16:9 available on a 1024 width, ie 1024 x 576, ( which seems the obvious choice );

- Or I can re-encode to 1280x720 ( 720p ). Now what's the point of that? Surely the ipad will just have to scale this on-the-fly to squeeze the 1280 down to 1024 ( and also correspondingly scale the height down ) so the resulting image will be the same size as the 1024 x 576, encode, but giving the iPod more work to do and also creating larger files.

I can't see the point of encoding it at 720p. Can someone tell me where my train of thought has become de-railed?

Perhaps the iPad has the option to watch the 1280x720 at 'almost full height' the whilst cropping the sides? Or perhaps the option for the iPad to play 720p to an external display?


--
SC

[jdobbs]

iPad output is limted to 1280x720 so you can't do 1080p. From the Apple iPad Specifications page:
TV AND VIDEO

Support for 1024 by 768 pixels with Dock
Connector to VGA Adapter; 576p and 480p with
Apple Component AV Cable; 576i and 480i with
Apple Composite AV Cable

H.264 video up to 720p, 30 frames per second,
Main Profile level 3.1 with AAC-LC audio up to
160 Kbps per channel, 48kHz, stereo audio in
.m4v, .mp4, and .mov file formats; MPEG-4
video, up to 2.5 Mbps, 640 by 480 pixels, 30
frames per second, Simple Profile with AAC-LC
audio up to 160 Kbps, 48kHz, stereo audio in
.m4v, .mp4, and .mov file formats; Motion JPEG
(M-JPEG) up to 35 Mbps, 1280 by 720 pixels,
30 frames per second, audio in ulaw, PCM
stereo audio in .avi file format

The reasons for encoding to 1280x720:

1. It is a standard HD resolution -- where 1024x576 is not
2. You can use the same encode for other purposes that use 720p.
3. Who cares how much work the iPad is doing during playback? What else is it doing?
4. I would also hope that since Apple makes an iPad component output that they will at
some point support HD output -- and HDTVs accept 1280x720. The VGA dock adapter
currently works at 1024x768 -- so if your HDTV has a VGA input (mine does), that can work.

But... if you're doing it for yourself -- use whatever resolution floats your boat. You can change it in BD-RB by adding another profile in ALTERNATE.TXT. 1024X768 (4:3) & 1024X576 (16:9) and other common ones are already there...

FYI: Main Profile, Level 3.1 allows a bitrate no higher than 14Mbs for video. So no matter what bitrate you choose, BD-RB will put a 13Mbs maximum bitrate limit on it (keeping a 1Mbs safety margin).

BTW: I have an iPad that I use for watching videos on flights and road-trips... love it. I usually just do them to 720x480 (NTSC) just to encode faster and limit the output size -- they look very good at that resolution. 720x480 is also a standard resolution.

[Stormcrow]

iPad output is limted to 1280x720 so you can't do 1080p. From the Apple iPad Specifications page:
TV AND VIDEO

Support for 1024 by 768 pixels with Dock
Connector to VGA Adapter; 576p and 480p with
Apple Component AV Cable; 576i and 480i with
Apple Composite AV Cable

H.264 video up to 720p, 30 frames per second,
Main Profile level 3.1 with AAC-LC audio up to
160 Kbps per channel, 48kHz, stereo audio in
.m4v, .mp4, and .mov file formats; MPEG-4
video, up to 2.5 Mbps, 640 by 480 pixels, 30
frames per second, Simple Profile with AAC-LC
audio up to 160 Kbps, 48kHz, stereo audio in
.m4v, .mp4, and .mov file formats; Motion JPEG
(M-JPEG) up to 35 Mbps, 1280 by 720 pixels,
30 frames per second, audio in ulaw, PCM
stereo audio in .avi file format

The reasons for encoding to 1280x720:

1. It is a standard HD resolution -- where 1024x576 is not
2. You can use the same encode for other purposes that use 720p.
3. Who cares how much work the iPad is doing during playback? What else is it doing?
4. I would also hope that since Apple makes an iPad component output that they will at
some point support HD output -- and HDTVs accept 1280x720. The VGA dock adapter
currently works at 1024x768 -- so if your HDTV has a VGA input (mine does), that can work.

But... if you're doing it for yourself -- use whatever resolution floats your boat. You can change it in BD-RB by adding another profile in ALTERNATE.TXT. 1024X768 (4:3) & 1024X576 (16:9) and other common ones are already there...

FYI: Main Profile, Level 3.1 allows a bitrate no higher than 14Mbs for video. So no matter what bitrate you choose, BD-RB will put a 13Mbs maximum bitrate limit on it (keeping a 1Mbs safety margin).

BTW: I have an iPad that I use for watching videos on flights and road-trips... love it. I usually just do them to 720x480 (NTSC) just to encode faster and limit the output size -- they look very good at that resolution. 720x480 is also a standard resolution.

Thanks.

So the reasons for encoding to 1280x720 are nothing to do with actually viewing it on the ipad screen. Like using the file for other purposes, standards compliance, and output to external displays. None of these apply to me.

In response to the 'who cares' point, I might argue that having the ipad re-scale during playback probably increases CPU useage and reduces battery life compared with not re-scaling, but I have no evidence to support this.

If my only desire is to encode for viewing on the actual device, then the 1024 option is probably better for me for smaller file sizes, and perhaps enhanced battery life. I have no need for the encodes for any other reason.

I'm not interested in adding custom profiles, just deciding between the 2 existing pre-defined ones.

I think I have enough info now to have decided on the 1024 encode for my purposes.

Thanks again,

--
SC

[Stormcrow]

OK, I've just gotten hold of my first iPad ( Xmas pressie for Junior ).

I have just synced the .MP4 of Percy Jackson which I re-encoded from the original BD using BD-RB Alternate Output Ipad 1024x576, and it works beautifully.

Thanks.

--
SC

[Dan Bernet]

I can't see the point of encoding it at 720p. Can someone tell me where my train of thought has become de-railed?Perhaps the iPad has the option to watch the 1280x720 at 'almost full height' the whilst cropping the sides? Or perhaps the option for the iPad to play 720p to an external display?

ipad2 smart cover (http://www.ebelow.com/ipad2-smart-cover-ipad-2-smart-cover-ipad2-smart-covers.html)
ipad 2 case (http://www.ebelow.com/ipad-2-case-iPad2case-iPad-2-cases.html)
ipad 2 covers (http://www.ebelow.com/ipad-2-covers-leather-ipad-2-covers-ipad2cover.html)

[jdobbs]

I can't see the point of encoding it at 720p. Can someone tell me where my train of thought has become de-railed?Perhaps the iPad has the option to watch the 1280x720 at 'almost full height' the whilst cropping the sides? Or perhaps the option for the iPad to play 720p to an external display?

ipad2 smart cover (http://www.ebelow.com/ipad2-smart-cover-ipad-2-smart-cover-ipad2-smart-covers.html)
ipad 2 case (http://www.ebelow.com/ipad-2-case-iPad2case-iPad-2-cases.html)
ipad 2 covers (http://www.ebelow.com/ipad-2-covers-leather-ipad-2-covers-ipad2cover.html) Look four posts before yours and I've already answered that question.

Encoding a other goofy resolutions in my opinion is... well... goofy.

[laserfan]

iPad output is limted to 1280x720 so you can't do 1080p... BTW: I have an iPad that I use for watching videos on flights and road-trips... love it. I usually just do them to 720x480 (NTSC) just to encode faster and limit the output size -- they look very good at that resolution.
Which seems the wisest solution IMO. When you think about the fact that most people can't tell the difference between SD and HD on sub-40" TVs where does that leave a tiny thing like the iPad?

But my wife told me I have to get an iPad2 so we'll see if I sing a different tune then! :)

[jdobbs]

Which seems the wisest solution IMO. When you think about the fact that most people can't tell the difference between SD and HD on sub-40" TVs where does that leave a tiny thing like the iPad?

But my wife told me I have to get an iPad2 so we'll see if I sing a different tune then! :)
Yeah, I've been very happy with my iPad. My wife now uses it as her primary device (her notebook PC has been filed in a drawer). I'll probably spring for a 16GB iPad 2. I've never even come close to using all the memory in my 64GB iPad 1.

[Capsbackup]

Yeah, I've been very happy with my iPad. My wife now uses it as her primary device (her notebook PC has been filed in a drawer). I'll probably spring for a 16GB iPad 2. I've never even come close to using all the memory in my 64GB iPad 1.

My wife is still quite pleased too with her iPad 1. Never uses the laptop anymore. We have tried a few different resolution movies, and I admit it is difficult to distinguish between them.
Having the choice of what resolution to encode to is perhaps the real key! ;)