Technical Questions regarding streaming

[diamond204]

Jake you're probably the guy for this, but anyhow...

From what I believe I have read previously is that Vudu in the past (and currently for older non replaced files) used several different source files for each film, perhaps one each for the quality levels - SD, HD, and HDX.

And in more recent years replaced with some form of perhaps single adaptive file that dynamically can adjust quality on the fly depending on the connection quality.

Correct me if I am wrong on the above.

My main question is: Is that new 'one file approach' used also for the UHD releases? So that the viewer of the UHD copy, HDX copy, or SD copy are viewing the same source file, just at different resolutions depending on what was purchased? And then if so, in theory, it would never be an issue with, for instance, the SD copy being a different aspect ratio than UHD, or a completely different non-remastered copy?

Same question with the Audio. Is it the same audio stream for all levels, just that the UHD copy will access the Atmos component (if available) of the Dolby digital plus file?

[Dive86]

Aspect ratio would depend on master given to Vudu by the studio HDX or UHD or 4K

[gamescan]

It's not really a "single file" in that there are typically multiple encodes. The video encodes should be preset at different resolutions and bitrates, with each of the encodes having the same keyframes. Automatic switching based on bandwidth should be done on a key frame, while the switching component should be controlled by the state of the playback buffer on your client device.

[echopulse]

What I want to know is are all the encodes based on the same Master.

[gamescan]

What I want to know is are all the encodes based on the same Master.

Assuming VUDU works like any other major VoD provider, they should be.

Studios will deliver the master file to the service provider. The service provider will then encode the content. Different providers will use different encoding "recipes," but most are all variations on FFMPEG.

A bad encode can be replaced by the service provider simply be re-processing the source. However, if the issue is in the source file, then the service provider can't do anything until that is replaced. As the old saying goes, "Garbage in, garbage out." A poor master file will never improve in quality, and you can see this in trailers of older films. Many of these are actually sourced from VHS copies since the original film prints for trailers weren't often archived by studios.

[Jake]

Vudu streams have always been multi-bitrate/adaptive - but at some point in the past lower resolutions ware added to HDX (some old devices do not support this, but every device sold in the past ~6 years should) allowing the bitrate to go significantly lower without buffering - effectively it makes manually switching from HDX to SD not that useful on supported devices, but that capability has been left in for now for consistency of experience across devices.

For the most part UHD uses a different master since currently all Vudu UHD is HDR (expanded color space and dynamic range), which is color graded differently from the SDR masters used for HDX/SD. Same with Atmos audio - currently Atmos is considered a "premium feature" on UHD - Atmos mixes are mastered differently from standard 5.1/7.1 surround (though it's likely the base 5.1 compatibility layer of Atmos is close to/the same as the discrete 5.1 mix).

[gamescan]

Same with Atmos audio - currently Atmos is considered a "premium feature" on UHD - Atmos mixes are mastered differently from standard 5.1/7.1 surround (though it's likely the base 5.1 compatibility layer of Atmos is close to/the same as the discrete 5.1 mix).

Unless VUDU is specifically ordering different 5.1 mixes, the base layer (under Atmos) should be the same as the standard 5.1 mix. It will be slightly different than the Atmos track encoded on Blu-ray discs, since those use Atmos on a TrueHD core, while VUDU (and other streaming services like Netflix) use Atmos on a DD+ core. Still, the way the stream information is layered across the two is similar.

A DD+ audio stream for a given movie on VUDU should be identical to the Atmos stream with the Atmos metadata stripped out.

[diamond204]

Thanks for the info Jake. It sounds like it is possible to have an older less superior encode as the HDX/SD file, as opposed to the UHD file.

As a sub question, if internet connection quality goes down while streaming the UHD file , is it possible that resolution could drop to HD? or whould it just prompt to switch over to the HDX file?

[Jake]

Thanks for the info Jake. It sounds like it is possible to have an older less superior encode as the HDX/SD file, as opposed to the UHD file.

As a sub question, if internet connection quality goes down while streaming the UHD file , is it possible that resolution could drop to HD? or whould it just prompt to switch over to the HDX file?

For new releases, I would say the HDX is not "inferior" other than the fact that it's 1080p SDR. For older library titles that are getting UHD the studios may have remastered specifically for the UHD release. We often re-encode lower resolutions if better sources are available, though, so I would say it's rare that the HDX is significantly different.

Currently Vudu UHD does go down to HD resolution at lower bitrates, but not quite as low as HDX, so It is possible if you can't reliably get more than ~4Mbps that you may have buffering and be promoted to switch. That may always change in the future based on the overall best experience of quality vs buffering, etc...

[gamescan]

For new releases, I would say the HDX is not "inferior" other than the fact that it's 1080p SDR.

It's impressive how much of a difference HDR vs SDR makes. It's much bigger than the 1080p -> UHD resolution jump. Even on a native UHD set, I would take 1080p HDR over UHD SDR.