My High Def Life: Exporting to AppleTV

by Erica Sadun

So I decided to give the new QuickTime 7.1.5 AppleTV export format a whirl. I wanted to find out what kind of size and bitrate would be produced by this QuickTime preset and see what kind of conversion times we'd be talking about.


I needed something pretty high quality to begin with so I started off in EyeTV with a relatively small (7 minute, 760 MB) High-Def recording. As you might recall from earlier articles in this series, EyeTV stores video as raw MPEG-2 transport streams. You cannot read these directly into QuickTime Pro, so you need a good quality intermediate format particularly because you cannot export directly to AppleTV in the current (2.3.3) version of EyeTV. I decided to export to 720p HDVideo as a first step and then use QuickTime to convert for AppleTV. For the curious, EyeTV's 720p HDVideo is 1280x720-pixels at 29.97 fps.


I then imported the several gigabyte result into QuickTime Pro and chose File -> Export and choose Movie to AppleTV from the Export pop-up. There are no further options or settings to customize the output. (The Options button is disabled and you can only use Default Settings.) Enter a name and click Save to perform your conversion. The conversion for this clip took over a quarter-hour on my 1.66 GHz Intel Core Dual with 1GB RAM. I gave up and hit "cancel" long before it finished on my aging 733 G4, but we were at over an hour at that point.


The resulting video looked very nice indeed. Clocking in at just under 200MB (about a quarter of the size of the original HD video, and way, way smaller than the intermediate HDVideo video), the quality was excellent. (You can download sample screenshots here.)


Details:


Format. H.264, AAC, 44.1kHz, 29.97fps


Data Rate. 3884.70 kbits/sec


Frame Size. 960 x 540 pixels



16 Comments

CrashRay
2007-03-13 12:06:17
Great ! Beautiul quality !
Heroes !!!!
Curious
2007-03-14 07:59:22
According to its specs, AppleTV can input and output 720p video. Although iTunes purchases are slightly less than Standard-Definition, there must be some way to get 720p HD video from a Mac to the Apple TV intact. Could you investigate?
nick
2007-03-14 10:01:34
yeah, it's kind of strange that it's 960x540, isn't it? why not just 720p?
retiarius
2007-03-14 11:17:07
960x540 for EyeTV -> AppleTV would reflect a limitation (feature) imposed by
the Image Constraint Token (ICT), whereby studio respect is paid to the
"analog hole", whereby no commercial HD material greater than 540p can go
through component outputs.


It's a bit more complicated, in that starting in 2011, analog out is contrained
further to "interlaced SD", thence to complete suppression in 2013.


Then there's the Digital Only Token, DOT, which turns off analog outputs in any player. See;


http://broadcastengineering.com/mag/broadcasting_cpr_redefined/

retiarius
2007-03-14 11:44:43
Re: that 540p limitation on EyeTV/MPEG2-originated material,
I retried the experiment with 1080p and 720p content (lossless animation, 30fps)
of my own design. Results? The QuickTime 'Movie to Apple TV'
setting transcoded them both to 720p, preserving the framerate.
siva
2007-03-14 13:53:57
Why is your frame size 960x540 instead of 1280x720? Hopefully, eyeTV will have a update that enables Apple TV export. I believe they almost have it ready since I got an email regarding that. I have an eyeTV hybrid. I don't think I will be buying an AppleTV version 1 though.
siva
2007-03-14 13:56:54
retiarius , I don't think image constraint token is at play here since this is OTA HD and not premium content. You can do anything with OTA HD. I have converted it at native resolution within eyeTV from MPEG2 TS to H.264 while preserving the framesize.
tji
2007-03-14 14:16:24
That's a bit odd that EyeTV converts 720p to 29.97fps for "HDVideo". The original 720p video should be the ATSC standard, which is 1280x720 @ 59.97fps. 1080i should be 29.97 frames per second (two fields combining together for a frame). Was the original source material 1080i?


Anyway, I find doing fewer conversion steps yields better quality. I have been doing HDTV MPEG2 to H.264 conversion with "MPEG Streamclip", and I've found it to be quite good. Since the AppleTV is not available yet, I haven't been able to confirm the resulting video works with it. But, it does work well with my Core Duo Mini connected to my HDTV.


tji
2007-03-14 14:24:39
Okay, I viewed the images.. Heroes, from NBC. So it was broadcast in 1080i, explaining the frame rate.


I'm still curious about the HDVideo intermediate step. What is that? Is it like HDV video camera format? Individual frame based video, like MiniDV except at higher resolution? If so, that seems like a big overhead of processing and disk space, and a source of quality loss.


Apple really needs to add better support for HD MPEG2 Transport Streams. Of course, they probably won't, since that would make it easier to "roll your own", rather than buying them through iTMS.

Erica Sadun
2007-03-14 16:57:03
I chose 720p HDVideo as my EyeTV export because I wanted a source that was at least as large as 720p AppleTV should be. I'm not sure why it was cut down to 960x540, especially when Retiarus (I hope I spelled that right!) was able to produce 720p.
dave
2007-03-15 07:15:27
So when I playback a commercial DVD on a computer, and send the output through the AppleTV for playback on my HDTV, it gets knocked back to 960x540 -- is that what happens?


OK, what software strips out the ICT data?

re: dave
2007-03-20 15:57:50
Dave, AppleTV does not play DVDs.
Dave
2007-03-21 10:27:03
Yes, I know that AppleTV does not play DVDs, but the Mac (or Windows) machine that drives it most certainly does. Anyone planning on creating a digital media library from (purchased) DVDs and scrolling through them via AppleTV isn't going to be very happy if the playback is significantly different from viewing the DVD via a set top DVD player.


And Siva, try taking your H.264-converted-from-eyeTV-MPEG 720p video and exporting it using QuickTime 7.1.5 into the AppleTV format. I consistently get the 960x540 format from all the over-the-air content that I record when I export to AppleTV. I think that the ICT tag is everywhere except older DVDs and consumer camcorders.


It remains to be seen whether the AppleTV will accept ANY video that is not in AppleTV format, and what the quality looks like when such video is compared to playback from the original DVD.

Mike
2007-03-23 14:52:46
The AppleTV needs a MPEG decoder up to ATSC standards. Transcoding or exporting from MPEG -> 264 is less than ideal, especially when it takes a 2-6x conversion time.


I'll wait for the next revision of the AppleTV. Maybe they'll figure out that ATSC tuners are becoming quite common. Or maybe Elgato will figure out to include a MPEG -> 264 transcoder into their next product.


I hate transcoding cpu cycles wasting away my Mac.

Zac
2007-04-19 12:21:55
OK once and for all look at the AppleTV specs...


They state AppleTV will play the following formats...


1280x720 @ 24FPS AVG bitrate of 5 mbps
960x540 @ 30FPS AVG bitrate of 5 mbps


It is converting to 960x540 because exporters will always choose to preserve the highest frame rate possible... If you feed the encoder 720P video at 24FPS then it will output at 1280x720... This is also true with the upgrade in EyeTV 2.4.... The first and foremost attribute of video that will be looked at is the framerate... if the framerate is above 24 it will downgrade to 960x540 in order to preserve more frames aka at 30 FPS... If the video is less than 24 it will then up the frames to 24 and preserve 1280x720 resolution

rolacel
2007-11-22 17:10:52
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