bvibber
commented
7 years ago A couple thoughts:
- Ideally, you want to run the entire WebM stream headers through the demuxer first, up to the first cluster containing data frames. Otherwise it won't initialize properly and will get confused when it finds packets with no header...
- The demuxer will not be happy at all unless it comes in on a predictable boundary, probably a cluster boundary.
- The video decoder can pick up from any keyframe, which should be predictably at cluster boundaries.
So you've got two basic problems to solve:
- Obtaining the headers to initialize the demuxer.
- Finding a cluster boundary on the input before feeding the new live data into the demuxer.
If you can serve out the header bits from a separate file or something that should work. If you have live streams with predictable formatting, you could probably pre-generate a header set too.
If you have pre-existing files you're serving out, you might benefit from using ffmpeg to generate MPEG-DASH manifests -- see http://wiki.webmproject.org/adaptive-streaming/instructions-to-playback-adaptive-webm-using-dash -- as that manifest file should list things like the size of the headers/'start codes'.
As for cluster boundaries, there should be a predictable bit pattern in the WebM/Matroska stream. See https://www.webmproject.org/docs/container/ etc for details on that; I haven't attempted this exact process so don't have a bit pattern handy to recommend. :)
AlexEKoren
Hey there, I've written my own subclass of OGVInputStream which reads from a TCP socket. It takes bytes as it comes in from the TCP socket and adds them to the buffer then presents them through the "readBytes: blocking:" method. I turn off seeking and I basically get a livestream as long as the server starts serving the WebM file from the beginning of the file.
However, the client may connect to the server in the middle of the WebM playback meaning it doesn't get headers associated with the file. Is there anyway to make sure the player waits for a Keyframe or something? Right now I'm getting a "nestegg_init" failed and then a "Error processing header state. :(" which I'm guessing occurs because it doesn't see the beginning of the file.
I'm not overly familiar with VP9 and WebM formats, but from what I've read it should be possible if the player is pointed at certain frames. I'm happy to wait for some sort of byte pattern and play from there or maybe there's a settings, I'm just not sure what to look for.