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JWort93

macrumors regular
Original poster
Aug 3, 2013
106
88
So I haven't seen this reported anywhere, but I was messing around with the developer Video HUD you can turn on if you plug your ATV4 into a Mac and load Xcode, and I noticed something interesting. When streaming an iTunes purchase on the Apple TV 4 from the movies or tv shows apps, the video bitrate was variable, shifting in a range of roughly 7mbps to 15mbps. This applied to both movies and tv shows purchased from iTunes, and is significantly higher than the roughly 5.6mbps constant bitrate that 1080p HD iTunes downloads are, when downloaded to a computer. This even matches or beats Vudu HDX streams. This doesn't seem to be the case for all titles though, I compared the movie Split, which I own on both Vudu and iTunes, and the Apple TV still streamed it at the regular 5.6mbps. I've also noticed that for movies and tv shows that stream between 7-15mbps, their stereo audio bitrate is 384kbps, whereas movies that stream at 5.6mbps have a stereo audio bitrate of 192kbps.

Has it always been like this?
 

TrackZ

macrumors member
Apr 16, 2010
88
17
I suspected this. If you have Dark Knight Rises in both iTunes and vudu, go to 53-54 minutes in both apps. Watch how and listen to how much better the iTunes playback is.

Watch the lights on Bane. Watch all the macro blocking and encoding noise on vudu that's smoother gradients on the iTunes version.

Audio is better too. Bass, dynamic range, and channel separation on iTunes are all stronger in the gunshots and the bat plane flying.

It doesn't make sense the iTunes copy would be better if you compare the bit rates of the download to vudu. Makes a lot of sense that the live iTunes playback is higher to create the quality difference.
 

jlasoon

macrumors 6502a
Jun 1, 2006
505
627
Orlando, FL
Now this is funny, just before my wife left for work tonight she asked me if iTunes had done anything to the movies. She said that a few of her movies looked a lot better. Brighter and clearer we're her exact words.

Didn't think too much of it until I saw this thread.
 

seanrt

macrumors regular
Jan 8, 2015
120
59
USA
Very interesting. I've fought with my inner video collector lately about watching from iTunes in the cloud and streaming the downloads from my iMac. When I first realized iTunes often offers new encodes of prior purchases I began to lean towards the cloud, plus it's just becoming a pain to manually manage my large digital collection.
I have my purchases all backed up but unless I manually check episodes now and then I wouldn't know a new encode was available. This new info is great to hear. I'm going to give my self a month trial just watching from the cloud and see how it goes.

*my one beef, I wish prior purchases (ones no longer available in the iTunes Store) would play from the TV App. I know in the public beta they recently started to show in the
Up Next line but still get error if I try to watch them from there.

JWort 93, thank you for this. I too am going to follow this thread as new info becomes available
 

Brenster

macrumors 6502a
Jul 7, 2008
794
787
Appreciate the post @JWort93

Having always collected physical media (VHS, Laserdisc, DVD, HD-DVD and BluRay (inc 3D) - not gone 4K yet), we've recently made the decision as a family to go for iTunes rentals & purchases (and Amazon where iTunes lacks) over physical media.

We've got endless amounts of physical media around the house, most of which is now redundant. Digital is proving to be 'good enough' both on the video and audio fronts. Looking into buying a new AV receiver as our current one is one the blink and started looking into streaming sound formats and bitrates (Dolby Digital Plus) vs the known quantities of DTS-HD MA, TrueHD and Atmos. The turning point was a rental of the recent live action Beauty & The Beast; the best I can say about the audio was that nothing about it grated, disappointed or called attention to itself relative to a potential BluRay purchase. Add in the convenience of streaming (iTunes Extras without finding & swapping out discs, iPad viewing for extras and films in the car etc) and the writing is on the wall.

Aside from iTunes listing films with DD+, there is remarkably little info out there in terms of audio & video codecs and bitrates for iTunes, Prime, Netflix et al.

Hopefully the increased clarity and definition @TrackZ is hearing on DKR is down to an increase in bitrate and/or switching to DD+; DKR is listed as 'Dolby 5.1' which I'm assuming to be vanilla Dolby Digital.

With better audio and video already poking through with iTunes streams, I'm really looking forward on what the next Apple TV can offer. Hopefully audio bitstream output of DD+ for external decoding and amplification as well has HEVC, 4K & HDR on the video side.

Apple have an interesting document on video and audio authoring/constraints for tvOS, iOS and macOS compatibility at https://developer.apple.com/library.../Reference/HLSAuthoringSpec/Requirements.html

Worth a read through.
 

Rigby

macrumors 603
Aug 5, 2008
6,235
10,180
San Jose, CA
So I haven't seen this reported anywhere, but I was messing around with the developer Video HUD you can turn on if you plug your ATV4 into a Mac and load Xcode, and I noticed something interesting. When streaming an iTunes purchase on the Apple TV 4 from the movies or tv shows apps, the video bitrate was variable, shifting in a range of roughly 7mbps to 15mbps.
Which field exactly are you looking at? Last I tried, the "HUD" only displayed average audio/video bitrates if I remember correctly.
I've also noticed that for movies and tv shows that stream between 7-15mbps, their stereo audio bitrate is 384kbps, whereas movies that stream at 5.6mbps have a stereo audio bitrate of 192kbps.
384 kbps is the bitrate Apple uses for the 5.1 AC3 tracks in most movies. The AAC stereo tracks should have 160 kbps. Some movies in the iTunes store also have DD+ 7.1 tracks (only when you stream them), but I have no idea what bitrate Apple uses for that.

But the most important question: Did you notice any improvement in image quality?

BTW, what would really excite me is if Apple started using H.265 not just for 4K, but also 1080p content. The quality improvement is often significant at typical streaming bitrates based on some experiments I did with x265 ...
 
Last edited:

TrackZ

macrumors member
Apr 16, 2010
88
17
One new data point. I live played Ant-Man, a right near 2 hour movie. My router reports the ATV consumed 6.37GB of data. The iTunes download for this is 5.01GB. So, there's a significant amount of extra data in the live playback, over 27% more information. That's worth some audio/video quality improvement for sure.
 

cynics

macrumors G4
Jan 8, 2012
11,959
2,155
I think this is just an "all in one" copy for all Apple devices vs a best quality copy specifically for your AppleTV on a fast network.

In tvOS 10 you can goto Settings > Apps > iTunes Movies and TV Shows and it has a video resolution modes independent of your SD/HD selection in the store.

In iOS 10 you can stream (vs downloading) movies. And in Settings > TV > iTunes Video you can adjust quality for WiFi and cellular independently and independent of SD/HD selection.

Clearly there is a lot of variables here that Apple can adjust for streaming to give the best quality based on user input, device being used, network speed etc.

If you use Handbrake a lot you may see the reasoning. If you are transcoding a Blu Ray for your TV you may use 1080p and closer to 1:1 settings, ending up with a high quality relatively large file. If you are transcoding a Blu Ray for your iPhone you''ll probably drop the resolution since its unnecessary and other things, ending up with a lower quality smaller file (that still looks good on that device). If you a transcoding for both you'll might compromise between them for that "all in one" copy. That "all in one" copy is probably the iTunes download. Whereas if you Stream it Apple knows the device and network speed and adjust accordingly.

Just my guess anyway.

I do find it strange that Apple would use CBR for their downloaded movies. Seems inefficient. OP what are you using to look at the bitrate for the downloaded content?
 
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