Cannot seek in TS

[Vicne]

Hi, all,

I guess this has already been discussed, but I cannot find any pointers to that. So forgive me if I'm asking stupid or already answered questions...

I have a project where I need to stream Transport Stream files and let the client seek through them (I don't need frame accuracy).
When streaming as a VOD video with VLC, seeking just doesn't work. Clearly, the problem is on the server because when streaming with the live555 server (after generating an index file), seeking works...

I am wondering if the problem is due to the same reason why no time information is shown when TS files are played locally in VLC (right of status bar stays on 00:00/00:00 during the whole playback). However, when played locally, one can always seek inside the file with the slider, even with no time displayed.

Strangely enough, in Windows Media Player, time info (both elapsed and total when seeking) is displayed, but seek doesn't work, while in SPlayer, both time display and seek work perfectly...

What I would like to know is :
- Are both problems linked (no time display and no seek ability) ?
- If so, what would be needed to get information from a TS. What relation is needed ? time to frame ? pcr to frame ? time to packet number ?
- If not, could stream seek be implemented the same way local file seek is ?
- Which are the modules involved in this problem and what kind of fix would be needed to solve it ?

I have some experience with video streams and I am a former C programmer (albeit almost exclusively coding in Java for a few years now), so maybe I can be of help...

Any hint or info would be greatly appreciated.

Best regards,

Vicne

[Rémi Denis-Courmont]

TS seek is implemented by linear extrapolation from the bandwidth.

VLC VOD is unmaintained and quite broken, so failure is not a big surprise here.

[Vicne]

Hi, Rémi, and thanks very much for your quick answer

TS seek is implemented by linear extrapolation from the bandwidth.[/quote

That's what I thought.
Extrapolation is more or less OK, I guess, so I wondered why it wasn't implemented in VOD

VLC VOD is unmaintained and quite broken, so failure is not a big surprise here.

Sorry to hear that.
I admit the website is rather misleading in this regard, because "Streaming" is one of the 7 top links on http://www.videolan.org/ and the related page gives the options of VLC and VLS as streamers, VLS seemingly being deprecated in favour of VLC without a mention of the feature being unmaintained or broken...

Can you advise me a good alternative server that would be able to stream TS files (including seek) ? Open source is preferred but closed source or commercial would be OK if needed.

Best regards,

Vincent

[Rémi Denis-Courmont]

Streaming (i.e. broadcasting) works great. It's only VOD which sucks.

[Vicne]

Hi, Rémi, and thanks again for replying

Streaming (i.e. broadcasting) works great. It's only VOD which sucks.

Ah OK, I thought streaming and vod were similar. Sorry :-/

OK then, I just did a quick test, and this way indeed I can stream a file, receive it on the client, and I can move the slider on the server to provide another section of the video to the client. So far, so good.
Now is there a way I can automate the seek (in other words, could the client drive the server to provide it with the stream beginning at a certain time ?

Maybe a word or two would be useful to explain my goal :
We transcode many files into TS, then they go through an automated content check system, and when they get rejected, a report is generated with offending timecodes so that an operator can watch the file and decide if it can still be accepted or not. What I would like to avoid is having the operator first retrieve the whole file via FTP before viewing it.
Instead, I would like him to to just look at a web page, click on a link and get the file streamed to him starting a few seconds before the offending part.
In other words, any solution that would only stream selected parts would do.

Do you think broadcasting would fit in this context ?

Best regards,

Vicne

[Vicne]

Now is there a way I can automate the seek (in other words, could the client drive the server to provide it with the stream beginning at a certain time ?

(Replying to myself ) : OK. The rc interface seems to do the trick perfectly : I can load a TS file and seek though it using a percentage notation, which is perfect (I'm amazed how much functionality there is behind VLC that I had no idea of for years ).

Now I may be looking silly, but the problem is I can't figure out how to stream the output via RTP or HTTP when controlling vlc via rc . No matter what I do, the file always opens and plays locally on the server.
Do I have to use command line options to redirect the output or do I have to do it through a rc command (and in this case, which one ?)

Any hint is appreciated.

Best regards,

Vicne

[Vicne]

OK. Don't know what I did wrong last time but it works now.
For those who are interested, here's a summary of my solution :
1) start a local VLC on the server, controlled via telnet (or rather raw socket) on port 12345, streaming as HTTP on port 8080 :

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vlc --intf rc --rc-host 127.0.0.1:12345 --rc-quiet --sout=#std{access=http,mux=ts,dst=0.0.0.0:8080}

2) connect to this control port 12345 (either programatically or manually, for example with a "raw" putty session) and start streaming the TS file by sending :

Code: Select all

add videopath\video.ts

3) start a client, for example a native VLC, and read the above stream :

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vlc http://localhost:8080

In the end, the client will be an embedded VLC (Firefox plugin), but testing is easier this way

4) now seek commands can be issued via the putty session on port 12345 ,such as :

Code: Select all

seek 95%

Note that only relative seek (%) is supported in TS, as in local playback via the standard GUI, but as total file length is known, it's easy to convert a given time into a percentage.

What remains to be done is the server code that performs the above steps 1, 2 and 4 when a browser requests playback from a certain point, but that's surely non-blocking. Ajax calls can be issued to seek to different points in the file.

Thanks to Rémi and all involved for both this great software and the helping hand.

Best regards,

Vicne