feat(rtsp): fix file descriptor exhaustion and memory fragmentation

[wafgo]

Previously, a new buffer pool was allocated for every received frame-sized package. This led to several critical issues:

• Excessive memory consumption: H264 frames have large variations in size, causing significant memory usage over time.

• File descriptor leaks: Each invocation of gstreamer::BufferPool::new() created a new socketpair, resulting in a steady increase in open file descriptors. This can be observed with:

  watch -n1 "ls -l /proc/PID/fd | wc -l"

  Over time, this would exhaust available file descriptors.

• Application instability: On devices such as the Lumus cam, memory usage would continuously rise (over 7-8GiB after 5 hours), eventually leading to a crash.

This commit resolves these issues by reusing buffer pools where possible and preventing unnecessary allocation of resources. This allocates a little bit too much memory for the frames, as it takes the next power of two for the buffer, but its worth it to stabilize the application

Tested-by: Wadim Mueller [email protected]

[jmoney7823956789378]

Seems like even the max buffer isnt large enough for some 4K cameras, as it filled instantly and still was unable to stream. I have 16 of them though, so maybe my use-case is an outlier.

[jsonn]

I've seen packets up to ~500KB as well, so it seems the 64KB size is too limited.

[wafgo]

Fair enough! I increased the Bucket size to 1M, hopefully this should be enough for all frames. But is this project dead? Looks like nobody is planning to merge this :(

[jmoney7823956789378]

@wafgo I'll give it a try today! Don't lose hope :)

edit: no luck, still running into an absolutely obliterated buffer even when testing 1 camera:

[2025-10-12T17:11:16Z WARN  neolink_core::bc_protocol::connection::bcconn] Reaching limit of channel
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] Buffer full on vidsrc pausing stream until client consumes frames
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] Failed to send to source: App source is closed
[2025-10-12T17:11:16Z WARN  neolink_core::bc_protocol::connection::bcconn] Remaining: 0 of 100 message space for 28 (ID: 3)
[2025-10-12T17:11:16Z WARN  neolink_core::bc_protocol::connection::bcconn] Reaching limit of channel
[2025-10-12T17:11:16Z WARN  neolink_core::bc_protocol::connection::bcconn] Remaining: 0 of 100 message space for 28 (ID: 3)
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] New BufferPool (Bucket) allocated: size=65536
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] Buffer full on audsrc pausing stream until client consumes frames
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] Buffer full on audsrc pausing stream until client consumes frames
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] Buffer full on audsrc pausing stream until client consumes frames
[2025-10-12T17:11:16Z INFO  neolink::rtsp::factory] Buffer full on audsrc pausing stream until client consumes frames
[2025-10-12T17:11:18Z INFO  neolink::rtsp::factory] Failed to send to source: App source is closed
[2025-10-12T17:11:18Z INFO  neolink::rtsp::factory] New BufferPool (Bucket) allocated: size=65536
[2025-10-12T17:11:18Z INFO  neolink::rtsp::factory] New BufferPool (Bucket) allocated: size=1024
[2025-10-12T17:11:18Z INFO  neolink::rtsp::factory] New BufferPool (Bucket) allocated: size=512

This is even after attempting const MAX_BUCKET: usize = 131072 * 1024; so I'm unsure if this means we need to go even bigger or if we're approaching it wrong. (I know nothing about rust)