J'ai trouvé cela sur le forum Anglais, très bon résume :

Okay, here's a guide I decided to make to get low latency in this game. If you follow these steps I guarantee you will achieve the lowest possible latency.
First of all here's how I think is the way to calculate actual latency in milliseconds from the settings in the rocksmith.ini file:

Multiply MaxOutputBufferSize by LatencyBuffer. Then divide by 48. Multiply by three. The result is output latency in milliseconds.

For example, say you have MaxOutputBufferSize set to 1024 and LatencyBuffer at 2.

Total buffer size: 1024 * 2 = 2048
Divide by 48: 2048 / 48 = 42.7 milliseconds
The latency is 42.7 milliseconds. If you want to know the specifics of the math, check this website: http://www.rme-audio.de/english/techinfo/lola_latec.htm

As I mentioned earlier, this is the output latency. You'll also have to take in consideration input and processing latency. Usually these are equal to each other. So, assuming this, to get total latency you just multiply the output latency with three; 42.7 *3 = 128.1 milliseconds.

As I said this is only how I believe it is calculated, if anyone wiser wishes to correct me, please go ahead.

Step one

Read the PC FAQ:

Make sure you have latest drivers for your audio device(s). Check the website of the manufacturer.

If you have many sound cards like me, you have to test and choose the best one. In my case, I had three different audio devices to choose from; a PCI Sound Blaster Audigy 2 ZS, M-Audio FastTrack USB and an integrated ALC889 in my motherboard. You'd think that the Audigy 2 would offer the best latency, but guess what, it's the worst. It just seems that the WASAPI drivers on the Audigy suck big time, the lowest latency I could go with the Audigy was 192 ms, which is unacceptable. With the M-Audio it was a little better, I achieved 129 ms. The absolutely best result was with the ALC889, with it I achieved a latency of 9.4 ms.

Step two

To change the latency settings for Rocksmith, you'll have to modify a file called rocksmith.ini (open it with Notepad). The file is found in the installation path of Rocksmith. In my case, it was C:\Program Files (x86)\Steam\steamapps\common\Rocksmith.

The parameters you want to look at are MaxOutputBufferSize and LatencyBuffer. Also, make sure that ExclusiveMode is set to 1 (has to be enabled for low latencies). MaxOutputBufferSize is the buffer size and LatencyBuffer is the number of these buffers. MaxOutputBufferSize will by default be 0, which means that Rocksmith will automatically choose the buffer size. From what I've read in the FAQ it seems it defaults most sound devices at a buffer size of 1024. Combine this with the default LatencyBuffer of 4 and you have a delay of 256 ms, which I find very high.

Okay, so where do we start? Well, I'd start with setting the MaxOutputBufferSize at 1024 and LatencyBuffer at 1. If this works that's great, you can now simply lower MaxOutputBufferSize until the the sound starts crackling in the game. I'd start lowering by 256 until crackling starts. Then go back to previous value and try lowering with 128, if that works lower by 64, then 32 etc. Do this until you are able to find the lowest possible value where the game works smoothly without losing audio or crackling or other anomalies. I achieved a value of 150 with my integrated audio device, which is quite a low latency and very playable.

If at the start you failed with MaxOutputBufferSize at 1024 and LatencyBuffer 1, try with buffer size at 2048. If that doesn't work, you'll have to start increasing the LatencyBuffer to 2 and then try again decreasing the buffer size.

Pro-tip: To fasten the process of testing, just wait for the intro sounds of the game and if they play just alt-tab and close Rocksmith and continue testing with lower buffer values. If you hear distortion or no sound, you know to increase the buffer.

Step three

This is a section of misc tweaks that might help you achieve a lower latency.

In this thread some have been able to achieve a lower buffer with the tweaks mentioned. I haven't tried these tweaks myself, but I recommend you try them if the current achievable latency is not low enough.

Another basic tweak is to close all unnecessary applications before playing Rocksmith, this includes applications in the task bar.
Also, make sure you have latest drivers for all your computer peripherals.

If you plan on upgrading computer parts, go for a faster processor as it will help with overall responsiveness. An SSD drive will also help in this matter. I can't currently recommend sound cards, since from what I've read and from my own experience it seems that integrated audio chips perform better when it comes to low latency. ASIO support in Rocksmith would be great, but I guess piracy would go rampant from that.

So that's it, hopefully you have now achieved a low latency and be able to enjoy the game! Please post if you have any other tips or tweaks you think I should add, or if you have any questions.
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