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Post by Micbarry on Aug 30, 2018 10:15:20 GMT
Hi there,
I have a question about using the Apple TV 4 as an Airplay destination from iTunes. My understanding is when you Airplay to an Apple TV, it resamples the audio from 16/44.1 to 16/48, as the device is primarily used for video, and 48kHz is the standard sampling rate for video.
I also understand that resampling can leave audible effects (correct me if I'm mistaken about this), depending upon how it is done/implemented.
This being said, has anyone performed a test to see if the 16/44.1 input matches the 16/48 output using the ATV4 specifically, or if it doesn't, are the differences audible?
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Post by Michael Lawrence on Aug 30, 2018 11:08:01 GMT
Hi Micbarry- What an interesting question. I wasn't able to find much information on the Apple TV and AirPlay protocols, but that's because I didn't look for very long  This might be of interest, and there's a discussion on the Apple forums here. Quite frankly, even if there is ASRC taking place, I would be absolutely stunned if it were audible. It would be easy enough to record the file back and null it against the original, but then you'd have OTHER stages of sample rate conversion in play and so it's difficult to say which stages would be responsible for any differences. I would guess that any audible differences in the null test would more likely be due to clock drift than actual ASRC "losses." Modern sample rate conversion is very, very good and I'm not aware of any data that shows people can readily identify the difference. If you come up with anything, let us know. We love that type of stuff here! |
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Post by Deleted on Aug 30, 2018 15:07:42 GMT
I wouldn't be worried, its upsampling, so theres no data loss. I've converted "HD" tracks 96khz/16bit(sometimes 24bit) to 44.1khz/16bit with free software called audio converter lite, found on apple store.
When i opened both converted and not converted files on DAW, flipped phase of another there was total silence. So for my understanding the information was all the same.
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Post by Michael Lawrence on Aug 30, 2018 20:47:52 GMT
I wouldn't be worried, its upsampling, so theres no data loss. I've converted "HD" tracks 96khz/16bit(sometimes 24bit) to 44.1khz/16bit with free software called audio converter lite, found on apple store. When i opened both converted and not converted files on DAW, flipped phase of another there was total silence. So for my understanding the information was all the same. Pasim- The data is not changed IF the sample rate conversion is "synchronous" - between simple integer sample rates such as 48 kHz to 96 kHz or the other way. Going from 44.1 kHz to 48 kHz, it's an asynchronous sample rate conversion (ASRC) and so the sample-to-sample data is changed. This does not mean that the result is necessarily audibly different, as you've pointed out. |
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Post by Micbarry on Sept 18, 2018 1:23:36 GMT
I've been doing a bit more A/B testing; albeit extremely unscientific. When a play the CD of a given track and then switch to the iTunes lossless version of the same track over Airplay via Apple TV 4, I simply cannot tell the difference.
Being aware that ASRC is taking place is sufficient to 'poison the well'/create a mental bias, but the differences simply do not exist...at least none that I can hear, even when I'm really concentrating.
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Post by Hexspa on Sept 18, 2018 22:07:17 GMT
I simply cannot tell the difference. Me neither. I converted some 44.1kHz multitrack synth files to 48kHz for a collaboration recently, and I was surprised at how transparent it was. Sure, they weren't acoustic instruments but either way I think the technology is there. |
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