Hi,
- I will play that file using my video editing suite, the EVM and
a Pandora and measure using a professional frequency analyzer. I will record that with a highspeed camera (both audio and video), so we can compare the frequencies of each system and also analyze the recorded audio output directly on a PC.
What is the input specification of the analyzer? Is it measuring the signals on a real (or virtual) 8 ohm or 16 ohm speaker connected to it? I ask because the TWL class D amplifier might not show the right signals if operated without a real speaker coil.
I can set that up. I'll start with standard Line Out signals, as they should have the exact same levels with the same audio file. (I hope the EVM also has a standard fixed line out as the Pandora has?)
Those should be fine to test the DAC, etc.
For the amplifier, I'll test the headphones port afterwards.
Or do you plan to drive a defined speaker with signals and do you measure with a microphone (resembling the tympanum and cochlea)?
I can additionally test it with a professional audio studio monitor and a Sennheiser ME66 (should be good enough for that).
I can then record both with a highspeed camera and test the latency.
Well, this is nice, but the human brain is very good at hiding or ignoring smaller latencies. So you might optimize something nobody can recognise.
When audio is delayed for more than 20ms, it's clearly noticable (20ms is about a frame in PAL) for trained people. I can easily see that (and if audio comes 10ms too early, it's even more noticable).
One thing that's important: You cannot compare TV to gaming. People in Germany are used to german dubbed movies, so when watching a movie, synchronity isn't that important. For sound effects: It depends. With explosions, you don't notice it, as most people haven't experienced in real life when exactly you can hear the sound of an explosion. Knocking on a door however is different - a 20ms delay, as mentioned, can easily be noticed.
With retro video gaming, this is different. Sound effects (jumping, shooting, etc.) are immediately connected with the user pressing a button. It feels weird if it's delayed - it can even make the game unplayable. I tried adding an artificial delay to Sonic and was way worse when playing it - as I'm used to the immediate jumping sound when pressing the button, so my control wasn't as accurate with a delay.
There will always be a bit of delay, I just want to check that it isn't too bad.
Most modern SoCs are meant for playing music, and gaming isn't as accurate as it was before (because all HDMI devices have a horrible video delay as well), so the delay is of low priority to the manufacturers.
What I mean is this:
http://www.hifi-forum.de/viewthread-42-38.html
They say +/-80 ms is unnoticeable. Well others disagree with that statement and we are not the first ones to think about it:
I know I can notice +10/-20ms, as synchronizing audio to video is something I do almost daily for over 10 years now.
"http://www.hifi-forum.de/viewthread-42-38.html
Gemäss den Angaben in den Richtlinien der ITU (ITU-R BT.1359-1 App. 1 [1998]) sind Asynchronitäten vom Durchschnittsfernsehzuschauer ab +45/-125ms erkennbar und bis +90/-180ms tolerierbar (plus bedeutet, dass der Ton dem Bild vorausläuft
Yes, I know that the game players are not „Durchschnittsfernsehzuschauer“ :) They are trained to have much better audio-visual sensors than the average…
For those tests to work we need a proper audio driver (without using a binary blob) for the TWL.
Would that be a suggestion?
Yes, looks good to me.
I can prepare the Panda-ES for speakers.
BR, Nikolaus