OVT over SRT transport: is it implemented or just planned?

[ysle]

Hi,

While reading the documentation and source code, I noticed a statement that caught my attention:

"The OVT is a protocol defined by OvenMediaEngine to relay stream between Origin-Edge and OVT can be run over SRT and TCP."

I dug into the source code to validate this claim. Here's what I found:

OVT Publisher (src/projects/publishers/ovt/ovt_publisher.cpp)

The publisher correctly uses port_config.GetSocketType(), meaning the socket type comes from configuration — so in theory, configuring an SRT port for OVT should be possible on the Origin side.

There's also this comment in the same file:

// It is only called when the OVT runs over TCP or SRT
// this version of OVT does not need to be considered because 
// it does not use UDP but only tcp or srt.

OVT Provider (src/projects/providers/ovt/ovt_provider.cpp)

However, on the Edge side (the client/pull side), the socket pool is hardcoded to TCP:

_client_socket_pool = ov::SocketPool::Create(
    "OvtProvider", 
    ov::SocketType::Tcp,  // hardcoded
    false
);

And in src/projects/providers/ovt/ovt_stream.cpp, only "OVT" scheme is accepted — there's no "OVTS" or SRT-based variant.

Questions:

1. Is "OVT over SRT" an implemented feature, or is it a planned/aspirational statement in the docs?
2. If it's not yet fully implemented (Edge side seems to be TCP-only), is there a configuration to enable it, or does the Edge OVT Provider need to be updated to support SRT?
3. Is there a planned timeline or roadmap item for completing the SRT transport support for Origin-Edge clustering?

The reason I'm asking is that SRT transport between Origin and Edge would be valuable for deployments where the inter-server link quality is variable (e.g., across public internet between data centers), as SRT's reliability mechanisms would help maintain stream continuity without adding a separate relay layer.

Thanks in advance for your help!

[cookesan]

Your reading matches the current source: the edge/pull side is TCP-only.

On the origin/publisher side, OvtPublisher::Start() creates the listening port with:

port_config.GetSocketType()

so the publisher side is socket-type configurable.

On the edge/provider side, OvtProvider::GetClientSocketPool() currently creates:

ov::SocketPool::Create("OvtProvider", ov::SocketType::Tcp, false)

and OvtStream::StartStream() only accepts the OVT scheme, allocates from that TCP pool, and sets TCP socket options such as TCP_NODELAY / TCP_QUICKACK.

The docs also show origin-edge <Scheme>ovt</Scheme> with normal origin.com:9000/... URLs; I do not see a separate SRT/OVTS scheme or provider-side SRT configuration path.

So based on current source, OVT-over-SRT is not fully implemented for origin-edge pull. The origin listener may have SRT-related plumbing, but the edge OVT provider would need implementation work to create/connect SRT sockets and a documented configuration/scheme for selecting it. I would treat the docs sentence as ahead of the implementation unless a maintainer points to another branch/config path.

[naanlizard]

Note this comment appears to be an LLM that took over a real person's account, and is spamming replies to presumably build rep.

Whether it is correct or not, be cautious

[cookesan]

Nope! It's just me :)

-cookesan

[cookesan]

and fair caution. I should have made the source basis easier to check.

The narrow claim I was making is only a current-source reading: the origin/publisher side appears socket-type configurable, but the edge/provider path creates the OVT client socket pool with ov::SocketType::Tcp, and the stream path I found accepts the OVT scheme and sets TCP socket options. I did not find a documented provider-side SRT/OVTS config path.

If there is another branch or config path for SRT on the provider side, I would follow the maintainers. I would not treat my comment as roadmap information, only as a pointer to the source locations that seem to make the edge side TCP-only today.

[naanlizard]

An hour ago you replied to a large number of different repos on random issues with wildly varying topics.

It's worse when you lie

[getroot]

In the past, OVT could be used based on SRT, but currently it operates only with TCP. This is because situations where packet loss between Origin and Edge is allowed have resulted in worse experiences in actual commercial environments. The comments and manuals are remnants of the past; I think they need to be corrected.

We intend to provide an option to select SRT-based OVT in the future, but it is not a high priority.

[ysle]

i see, thanks for the info.