Recording subtitles

[Ford1]

no, not related to sync issue, but as the op never stated the programs he was suffering with, this could have been the problem he was facing all along?

 

[paulab]

Hi. It was not a live progamme problem, Ford1. We never use subtitles with those because of exactly the problem you have highlighted.

The problem I have experienced is with Free-to-Air Freeview. I am on the Crystal Palace transmitter. The only subtitles available are DVB, at least for every channel I have tried them on. Out of the box, (Miraclebox Premium Twin Plus+ with the latest OpenVix) none of the recorded subtitles were correctly synced with video -- and that was on BBC1 as well as others. For one Channel 4 recording, I needed more than 20 seconds of delay to sync them. Since OpenVix only allows up to 20 seconds, it was therefore impossible.

The box has gone back now. I am afraid I do not have the patience to set about syncing each channel individually as I switch from recording to recording. Perhaps I am unique in experiencing this issue and there was a problem with the way my box was set up. But, as I said, it appeared to be there from the outset, even after a factory reset.

PaulAB

 

[adm]

In the last hour I've recorded a series of 10 minute program snippets from various channels on Freeview (Bluebell Hill Transmitter). All the DVB subtitles seem to be near as makes no difference in sync using the default Vix settings. When I checked the other night the same was true for recordings made from satellite (Freesat channels). I have two of each tuners in my Extrend.

 

[Rob van der Does]

If changing the delay-settings makes no difference, that means that the titles actually do have a time stamp.

 

[ccs]

I had a quick try this morning and found that bbc2, itv, ch4 broadcasting "live" (pre-recorded HD) was 100% fine.

A bbc1 HD recording from last night was about 5 seconds behind. (Belmont freeview.)

That was as far as I got. Default settings used.

 

[paulab]

One this I did not check, because it never occurred to me, was if the problem was affected by the aerial source. My aerial feeds into a Humax and then out to the TV. I simply disconnected the TV and connected the humax aerial out to the Miraclebox. I would not have thought that could have any effect. Could it? I have had two UK freeview boxes in series before and never noticed and issue.

Is there a different may of handling subtitle timing on recordings? Of the two Freeview boxes I have had extensive experience with, the Topfield 5800 never showed any timing issues with subtitles on any channels during more than ten years, so far as I can recall. The Humax (HDR2000T) is fine on BBC but it has issues on some other channels. (But that is of a different nature. The subtitles sometimes rush ahead as if they have lost their way, but they eventually sync again -- usually). That would suggest to me -- if timing is the problem -- that Humax and Topfield have found a way to deal with recordings with poor timing signals without ending up with a delay.

PaulAB

 

[Rob van der Does]

Just to make clear what happens: all Enigma2-STB's record the complete TS (transport stream), so that includes all (audio/video/data) what the provider has mixed in his transmission.
e.g. when the provider supports TeleText, that's also available during playback. And the same applies to subtitles.
BBC (1/2/3/ SD/HD) has both DVB & teletext subtitles: I use them all the time and they work perfect. The TeleText subtitles are the ones you should use, as E2 does a perfect job in grabbing them and displaying them exactly as you want, while DVB-subtitles are just graphical overlays in which we can only change the colour.

The problem with subtitles is, that the provider sometimes send them without a time stamp (or with wrong time stamps). That means they are not ordered to show at a specific time or at the wrong time. During live-TV this is not a problem: they will be shown at the very moment they are received, which will be correct most of the time. But during playback the lack of timings play havoc, as you've seen yourself. BBC used to be very good in this respect, but lately they tend to 'forget' the timings. IMHO a matter of quality control.
But: the good news is that ViX allows you to correct that (although the correction can be different per show). Just play around with the delay settings ...

It is indeed possible that FreeView/Sky/Freesat/Topfield (and possibly more) STB's are not hampered by subtitle timing issues. They are 'closed source' devices, which means that the manufacturer has all the ins and outs of the complete SoC and the way a TS is handled. That means amongst others that they can look into the demuxer, and actually add a timestamp (i.e. the moment the titles are received). As you may know all STB's we support have closed source drivers, so we are not able to do the same. We just have to rely on what the SoC actually does when saving a TS.

 

[paulab]

Would it be possible for OpenVix to gain access to any of the closed source drivers in order to be able to add a time stamp?

There is another solution, used I think by Panasonic on its Freeview boxes. When you schedule a recording the software asks if you want subtitles. If you select them then the subtitles are 'printed' onto the recording, like subtitles on a foreign language film. Afterwards, they are always on, but they are synchronised. Would it be possible to implement a system like that in OpenVix.

PaulAB

 

[Rob van der Does]

Would it be possible for OpenVix to gain access to any of the closed source drivers in order to be able to add a time stamp?

No; that's by definition impossible for closed source...

There is another solution, used I think by Panasonic on its Freeview boxes. When you schedule a recording the software asks if you want subtitles. If you select them then the subtitles are 'printed' onto the recording, like subtitles on a foreign language film. Afterwards, they are always on, but they are synchronised. Would it be possible to implement a system like that in OpenVix.

Sounds extremely invoking to the existing functionality, and certainly not something that can be done by a hobby-team. And besides: does the Panasonic ask which titles should be kept that way? Some services have subtitles for over 10 different languages (obviously a Freeview-only box will not be hampered by such a service).

 

[ccs]

I had a quick try this morning and found that bbc2, itv, ch4 broadcasting "live" (pre-recorded HD) was 100% fine.

A bbc1 HD recording from last night was about 5 seconds behind. (Belmont freeview.)

That was as far as I got. Default settings used.

Just a minor update.

The bbc1 HD programme I referred to was infact the Graham Norton Show.
Not only were the subtitles 5 seconds slow, but, in the main, they were appearing in single words rather than sentences or phrases.
Almost impossible to follow.

I've now recorded last nights show in HD and SD, and both recordings are pretty much in sync, maybe a second behind.

Other bbc1/itv recordings I've tried are pretty much 100% ok.

 

[Rob van der Does]

JThe bbc1 HD programme I referred to was infact the Graham Norton Show.
Not only were the subtitles 5 seconds slow, but, in the main, they were appearing in single words rather than sentences or phrases.
Almost impossible to follow.

That sounds like live-subtitling.
Imagine how fast people have to type, to get this result (even if it's not appreciated by you). And sometimes it includes translating as well.

 

[ccs]

That sounds like live-subtitling.
Imagine how fast people have to type, to get this result (even if it's not appreciated by you). And sometimes it includes translating as well.

It was a pre-recorded programme which I then recorded, so no "live" element to the subtitles.
Having said that, I suppose they could have been added live, but I'd be very surprised if that was the case.

 

[Mickkie]

It was a pre-recorded programme which I then recorded, so no "live" element to the subtitles.
Having said that, I suppose they could have been added live, but I'd be very surprised if that was the case.

Yes, they would be live subtitles - they were generated when the program was originally transmitted, in real time. Retransmissions of the program use the same subtitles from what I have seen. Just like when watching news programs, the subtitles invariably end up being spat out on the screen like a gatling gun, a word at a time, sometimes half a sentence. Impossible to follow reliably unless you won the speed-reader of the year award.

The Topfield 5800 did not have a problem with live subtitles as has already been mentioned. I suppose a solution to this could involve buffering the subtitles stream and then printing them on-screen a sentence at a time. When I stream from Mut@nt to a PC of a live program and play the stream with mpv or vlc, I don't get this word-@-a-time problem. So I assume this is something to do with onboard video player settings, or the memory constraints of the Mut@nt.

 

[simonc]

I'm glad you've mentioned the live subtitling issue, as I have the same problem, on top of the same timing issue seen by Paul. The gatling gun style live subtitle issue is a bug in OpenVix, whereas the latter is specific to the proprietary drivers shipped with specific boxes, so is limited to certain models. In my case an XTrend ET8500. Do you have a Mut@nt HD51, Mick? (and Paul if you happen to still be around!)

I'm putting a patch together for both bugs, although working around the driver bugs will break the handling of badly timed subtitles on the Travel Channel, which was important enough to someone to fix a few years ago.

 

[Mickkie]

Yes, I have a Mut@nt HD51 with freeview tuners. I do not experience the problem paulab described with subtitles getting out sync. The subtitles on films and documentaries (i.e. pre-recorded programs) appear as they should, in sync and in full sentences. I only have a problem with live transmissions, e.g. news bulletins, where they appear in gatling gun style, with some words and parts of sentences disappearing within milliseconds. Changing the delay for subtitles does not seem to make a difference with this live transmission problem. I'd be grateful for a fix.

 

[ronand]

That's the way they are on live transmissions - there's nothing to fix.

 

[simonc]

I beg to differ. The live subtitle code has a subtle bug that means it doesn't match the DVB spec in a couple of important places. Have a look at this video

[URL]https://photos.app.goo.gl/p7aSFnfNNTH4j6XF6[/URL]

and you'll see that live subtitles are pretty much unreadable. What should happen is that single word subtitles should add to the previous words on the line until there's no more space, then that line should be readable in full when the next line starts filling. What we have currently is not the correct behaviour. Note that you don't see this behaviour when they read the headlines on the news as these seem to be fed from the same system as the newsreader's autocue or when they're playing a report.

 

[Mickkie]

I'm currently on OpenVix-5.2.037 and noticed the unusable subtitles 'gatling gun' problem on live transmissions has gone away! Now the subtitles appear on a couple of lines at a time and persist long enough to allow reading them. This is both when watching live and when playing back a recording of a previously live transmission. I tried it on BBC News - I assume other channels will behave the same. I don't know if someone changed the code to achieve this, or if it happened as a side-effect of some other code change - either way I am a happy camper and thankful for the result.

 

[ccs]

No accident...……

https://github.com/OpenViX/enigma2/pull/401

 

[Mickkie]

No accident...……

https://github.com/OpenViX/enigma2/pull/401

Grateful both to Simon for fixing it and Abu for merging it. Pints await whenever you're in the area! :beer_toast: