MPEGTS seeking capability

[amoussawi]

Hello...why isn't possible to seek a MPEGTS stream? MPEGTS is providing a great advantage for my application but the drawback is that I'm not able to seek. My case is that I'm streaming MP4 through UDP, and some packets might get dropped so instead of re-transmission I replace the dropped frame by an old frame but doing this is causing problem with Exoplayer(the video doesn't even play) unless I used MPEGTS container format where it distorts as expected but at least it continues playing.

[ojw28]

Unlike containers such as MP4, MPEG-TS doesn't contain an index structure to allow seeking (i.e. a structure that allows mapping from time->byteOffset). Hence seeking in an MPEG-TS stream requires the player to either download the whole stream, scan it and build an index itself, or to guess based on average bitrate assumptions. We've decided to only support seeking in container formats that are properly designed to support it, which MPEG-TS is not.

As an aside, note that seeking is possible in HLS, even though it uses MPEG-TS, because in HLS a separate media playlist is provided to serve as an index structure.

It seems strange to be using UDP for seekable streams. What's your use case exactly? Why don't you just use MP4 over TCP? It's not valid, in general and for any container format, to replace dropped frames with other frames taken from the stream.

[amoussawi]

I will take a look into HLS if I could do a work around.
Well it will only be possible to seek backward and not forward using a cache.
I'm replacing frames because I cannot skip frames, and I guess this should be the case when live streaming, and my case is that I'm not using a media source from which to request the data at anytime, request happens only once and then data transmission starts through UDP until end of stream is reached.

[Avetri]

Indexing of TS files there are In solutions like DVR. So, if somebody would be so interested, an indexer might help.

[amoussawi]

Actually I already worked on it and used PCR value in the TS packet header for indexing. You can take a look at it on pull request #1274

[ojw28]

Now supported in dev-v2.