Anyone? I might be able to test this out on Friday. I'll post here...
- 37 Posts. Joined 10/2007
- Location: Ontario, Canada
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I'm not sure if this is the right place to ask, but did anyone try streaming music from their iDevice to the apple TV using Airplay?
I did and i find the SQ is inferior when streaming from my iPod's music player to the apple TV in comparison to streaming iTunes from my mac computer to the apple TV and i wonder why.
In both cases I am using the same .wav files and the apple TV optical out is connected to my DAC. I assumed the bitstream (1s & 0s) would be identical/bit perfect in both scenarios but it doesn't appear to be the case...are all bitstreams not created equal?
Thanks in advance for any input/explanation.
Note: All playback settings in iTunes such as crossfade, equalizer, etc. are disabled.
even bit-identical audio data signals can "sound different" after d/a conversion if jitter affects the quality of the d/a conversion process. Different cables, lengths, and transmission protocols can affect jitter issues differently, which in turn can affect d/a conversion. Jitter doesn't affect bit accuracy, but it affects *when* each digital sample is converted to analog voltage... which affects how your ears perceive the resulting waveform.
Thanks for responding and sharing your thoughts. In my case both data streams (iTunes from mac & iPod music player) are transmitted wirelessly to the Apple TV device with a common optical cable between the ATV & DAC. Therefore, the "net" A/B comparison is between the two bitstreams. Thanks for reminding me about jitter, i guess that is what is responsible for the differences i hear. I suppose it makes sense that a portable device such as an iPod would have higher jitter rates...
DanBa - Thanks you as well for your thoughts on jitter, that is most likely the reason for the audible difference.
As far as I understand, the audio jitter is not involved in your AirPlay cases.
From the Mac/iPod to the DAC of the Apple TV, there are two different streams:
. computer networking stream: from the Mac/iPod to the audio player of the Apple TV
. digital audio stream or PCM stream: from the audio player of the Apple TV to the DAC of the Apple TV.
The audio jitter which affects the D/A conversion is only involved in the PCM stream.
Audio jitter is an attribute of PCM digital signals, particularly clocks that impart the timing to the data that is being moved from the player to the DAC.
In the AirPlay iPod case, I think there are some computer networking losses (iPod CPU not able to fill the sending buffer just in time ?, not well-formed iPod transmission waveforms ?, mismatching of iPod sending buffer size and Apple TV reception buffer size ? …)
"Streaming is a method of delivering data to a device in a piecemeal manner. Rather than retrieving the whole file, the renderer fetches only a small portion of the file then starts playing immediately. Within the DS (or Apple TV) is a small reservoir, or buffer, containing the next few pieces of the file, in a queue ready to be played. The buffer is kept topped up, while audio is playing, by retrieving more data from the network. The buffer allows the audio to continue uninterrupted in the event of any brief dropouts in the network delivery. It also allows the audio to be faded out slowly in the event of any long term network interruption."
It won't ever work. The accessory exists only because the iPad didn't have a camera and the phone did. For this reason, Apple probably will never support the phone.
I think we need a device that says the following:
Device: Let me in and at the music data
iPad: No way. You have not yet anted up and made Apple even richer.
Device: Suit yourself. I will now go to connect with an Android device whose music files are up for the taking.
That's the dialogue I am looking forward to.