Question about memory cache and FPS

[Suwan]

Hello everyone

Recently I found out that, when I start capture, the number of the frames in use(memory cache) rising rapidly.
When the number hits the top(memory cache full), the FPS would fall to about 2 or 3 from 45 with a large amount of dropped.

My equipment is:
Player One Uranus-C (IMX585)
SharpCap Pro 4.0.9545, 64 bit
Windows 10/8g RAM/128G SSD
High Speed Frame Cache sets to 2760Mb(Max)

Capture Setting:
Output Format: AVI (I've tried SER but still the same)
Capture Area: 3856x2180
Colour Space: RAW8
Frame Rate Limit: Maximum
USB speed: 100

The attachment is an example:
At the beginning the FPS is 45.9, memory in use already reached 30
In the middle, the frame in cache rising quickly, but the FPS keeps 46
When the cache is full, the FPS fall to 2.5 with 26 dropped

In my understanding, when the cache is full, the frame will be written directly into SSD through USB cable right?
I also test the speed of my SSD, the written rate would be over 400M/s
Single frame about 4K resolution is about 8M, So I think the FPS won't be that low even if the cache is full.

Anything I can do to improve? or do I miss something?

Thank you for your help!

[admin]

Hi,

the frame cache only fills up if the SSD or HDD you are writing to cannot keep up with the data flow rate from the camera. That sounds as though it is happening in your case, so frames from the camera will go into memory (at the same time, SharpCap is writing the frames to SSD as fast as possible). When all of the memory is full then the capture frame rate drops to the rate that the SSD can support - basically frames from the camera have to be discarded until a memory slot is freed up by writing one frame to SSD, then one more frame goes into memory and it repeats.

There is a 'Speed Test' button in the filename settings that just writes fake image data to an SER file (6Gb worth) and times it to give you an idea of how quickly your SSD can accept data. Sometimes the rates can be much lower than the theoretical speed of the SSD, particularly if

* The SSD is close to full

* The SSD has not been 'trimmed' recently.

To get the best results it is a good idea to make sure there is plenty of space on the SSD and to run the 'Optimize' process in Windows disk tools - this optimize process trims the disk, meaning that it makes sure that all the space not currently in use is erased and is ready to be written to.

cheers,

Robin