The BlastCodec client-side image caching mechanism stores pixel content on the client to avoid re-encoding and retransmission. This feature is enabled by default to reduce bandwidth usage.
The BlastCodec image cache stores in dynamic memory previously displayed screen content that can be reused within the same or future frames wherever the same pixel content is displayed again. For example, when you switch between applications or browser tabs, any screen content that was previously displayed might be pulled from cache if available, avoiding re-encoding and retransmission, thus saving compute and network resources. When new screen content is found in the cache, only small table indexes are transmitted instead of bigger payloads with pixel data.
For typical office workloads, the use of image cache has reduced network traffic by more than 50%. In LAN connections this might yield small gains but in WAN connections with constrained bandwidth the use of image cache proves to dramatically improve user experience and provide a smooth and responsive desktop experience.
Image Caching Lifetime
The image cache resides in dynamic memory that is allocated at runtime and automatically cleared when the Blast session is closed. You do not need to perform any manual steps to clear the cache.
BlastCodec Cache Size
By default, this feature is enabled, so that the client/agent stores portions of the display that were previously transmitted. The default cache size is 250MB. A larger cache size reduces bandwidth usage but requires more memory on both client and agent. A smaller cache size requires more bandwidth usage. For example, a thin client with little memory might only accommodate a smaller cache size.
Configuring the Cache size
Windows HKLM and GPO
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EncoderImageCacheSizeKB
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EncoderImageCacheEntries (defaults to 400)
Linux
-
RemoteDisplay.updateCacheSizeKB
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RemoteDisplay.updateCacheSizeEntries (default to 400)
Cache Size Limitations
Actual cache size allocated might be lower than configured and is subject to agent and client system memory, screen resolution and monitor count. For cache sizes bigger than the default, the client also needs to be configured to allow higher limits by using the config RemoteDisplay.updateCacheSizeKB in the respective OS config file location:
Windows
%APPDATA%\Omnissa\config.ini
Linux
/etc/omnissa/config
Mac OSX
~/Library/Preferences/Omnissa Horizon Client/config
Blast Codec Image Cache Compression
Image Cache compression has been available since Horizon 2406. This technique is enabled by default and aims at reducing agent-side memory consumption resulting from the use of Image Caching. This is achieved through real-time and lightweight compression techniques that show memory savings >50% for VMBlastW without any performance penalty.
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