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Roberto Lombino

Playing two audio tracks simultaneously (intended for audio description)

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Roberto Lombino

Hello. I live in the Czech Republic and I have been using DVBViewer for more than three years. As I’m blind, I really like all the accessibility features included in the program. 
The only thing I miss is the support for audio tracks with audio description (AD). As far as I know, the AD can be provided by a TV channel in two ways: 
1. Broadcaster mix – a dedicated audio track, which includes the original sound and the description. This method is used f.ex. in Poland and Italy. 
2. Receiver mix – the audio track only contains the description itself and the receiver has to play two tracks simultaneously. This is how all Czech channels provide the AD and as far as I know, it looks similar f.ex. in the UK. Now, with the current version of DVBViewer, I can only listen either to the original sound or to the AD itself, which makes no sense. 
Would it be possible to implement an option to play two audio tracks simultaneously so that the user could choose which two tracks should be played? In the menu, the option could be called e.g. Secondary audio track and it should also contain a default option Off or Disabled. 
Or, if you have another idea how to solve this problem in a better, more sophisticated way, could you try to implement it, please? 
Thanks very much.

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Griga
vor 32 Minuten schrieb Roberto Lombino:

2. Receiver mix – the audio track only contains the description itself and the receiver has to play two tracks simultaneously. This is how all Czech channels provide the AD

 

I have never heard of it before. All channels that I know are using the broadcaster mix, particularly German and UK channels (at least over satellite).

 

Nevertheless I will think about it. Maybe an easy way to provide the recceiver mix is the picture in picture feature of DVBViewer. Up to now It only allows either main window audio or picture in picture audio, but not both, assuming that nobody wants to hear audio of two channels at the same time. However, both playing the same channel, but different audio tracks, could be a solution in your case.

 

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Roberto Lombino

Yes, that could be a good solution. Thing of it and if possible, implement it please. It would be very helpful.

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Roberto Lombino

Yes, you’re right. Via satellite British channels have a track with both (broadcaster mix), but on the terrestrial TV they use receiver mix. If you want to have a material for tests, I can record a piece of a program with AD from the Czech television and send you a cloud link.

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Griga
vor 13 Stunden schrieb Roberto Lombino:

If you want to have a material for tests, I can record a piece of a program with AD from the Czech television and send you a cloud link.

 

That would be good anyway. I'd like to include it in my sample collection.

 

However, the idea to use the picture in picture function for a receiver mix audio description doesn't seem so convincing at last. It would cover live TV, but no playback of recordings. Besides that, using two separate playback chains may lead to synchronization problems after some time and also after seeking / jumping in a file.

 

The main problem is that the basic playback components are not designed for playing two audio tracks at the same time. This applies to the DVBViewer Filter as well as to third party components like the frequently used LAV source filter. They would need two audio outlets, but they only have one.

 

Is there a media player that provides a receiver mix option?

 

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Roberto Lombino

Unfortunately, I don’t know much about this on this level. The only thing I can tell you is that there is a simple Czech app called Holz TV, which uses VLC for playback and which can record a TV show with the AD using receiver mix. However, this program is very simple in the technical sense (f.ex. if you want to watch TV with the AD, it simply opens two instances of VLC, each of them playing a different audio track).

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Roberto Lombino

I’ve recorded a piece of a TV series from the 1st channel of our public television with all audio tracks. You can download it here: https://www.dropbox.com/s/eo72a725ym0mdul/11-14_20-09-15_CT 1 HD T2 (AAC%2Ccze)_Rapl%2C Tichá voda - 11 13 Zdá se%2C že drsnější než Krušné hory může být jen Kuneš. Detektivní série s Hynkem Čermákem v hlavní roli. Dále hrají L. Příkazký%2C A. Pyško%2C L. Žáčk.ts?dl=1
Besides that, here’s a link to a document with technical data of our AD. It’s in French and English. Everything should be the same except for the language of the AD track in brackets, which in France is (qad), whereas in the Czech Republic it’s simply (cze), the same as the main track. http://www.cgvforum.fr/cgv_kds/pub/specifications/CSA_Signalling-Profile_v3.3.pdf
If you find a way to implement it, please leave also an option to play the AD track separately as it’s now, because sometimes, due to a technical error f.ex. on satellite, a track can be signed as the AD receiver mix, although it’s not.

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Griga
vor 7 Stunden schrieb Roberto Lombino:

The only thing I can tell you is that there is a simple Czech app called Holz TV, which uses VLC for playback and which can record a TV show with the AD using receiver mix.

 

That's interesting. VLC is no DirectShow based player like DVBViewer, but uses its own built-in playback system. So  I've searched the web for a possibility to play different audio tracks simultaneously in VLC. It cannot be configured in the user interface, but by using a command line:

 

start "" "C:\Program Files (x86)\VideoLAN\VLC\vlc.exe" --sout-all --sout #display

 

More information can be found here:

 

https://forum.videolan.org/viewtopic.php?t=145140

 

I made a batch file named VLC.bat that only contains the command line above, which is suitable for the 32 bit version. After launching VLC with this batch file it plays all audio tracks that are contained in a TS file simultaneously. And even more: If I give VLC the address of a TV live stream delivered by the DVBViewer Media Server, it also plays all audio tracks simultaneously.

 

So the best solution that we can get with available means seems to be a combination of the DVBViewer Media Server and VLC. You can buy the DVBViewer Media Server for 19 Euro. It is a background application running as Windows service. It has no user interface on its own, but provides a web interface in the browser and is designed for background recording and delivering  live streams and files to clients like the VLC.

 

However, this solution still requires some thoughts about how to make it usable for someone who is blind...

 

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Roberto Lombino
40 minutes ago, Griga said:

 

That's interesting. VLC is no DirectShow based player like DVBViewer, but uses its own built-in playback system. So  I've searched the web for a possibility to play different audio tracks simultaneously in VLC. It cannot be configured in the user interface, but by using a command line:

 

start "" "C:\Program Files (x86)\VideoLAN\VLC\vlc.exe" --sout-all --sout #display

 

More information can be found here:

 

https://forum.videolan.org/viewtopic.php?t=145140

 

I made a batch file named VLC.bat that only contains the command line above, which is suitable for the 32 bit version. After launching VLC with this batch file it plays all audio tracks that are contained in a TS file simultaneously. And even more: If I give VLC the address of a TV live stream delivered by the DVBViewer Media Server, it also plays all audio tracks simultaneously.

 

So the best solution that we can get with available means seems to be a combination of the DVBViewer Media Server and VLC. You can buy the DVBViewer Media Server for 19 Euro. It is a background application running as Windows service. It has no user interface on its own, but provides a web interface in the browser and is designed for background recording and delivering  live streams and files to clients like the VLC.

 

However, this solution still requires some thoughts about how to make it usable for someone who is blind...

 

Well, this could theoretically be a solution, but:

1. VLC has its own processing which can’t be turned off in a simple way.

2. As you will see in my sample recording, there are often more than two audio tracks in one TV channel and in that case your idea won’t help at all.

3. I think it shouldn’t be necessary to buy one more product (in this case, the media server) just because of the audio description format.

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Griga

1. I don't understand.

 

2. Please follow the link to the VLC forum that I have provided above. Someone posted:

 

Zitat

Then there is an interesting behaviour: If I disable the audio in VLC menu, then I can add audio tracks one by one.

 

I have just tried. It works. So you can still select the audio tracks that you want to hear.

 

3. I think it should not be necessary to do additional and quite laborious programming just to fulfil a single request. Up to now you are the only one. You don't want to spend 19 Euro for a DVBViewer add-on, but you expect us to spend hours and days with implementing what you want? I don't like this kind of demanding behaviour.

 

Please note that I'm dealing with your request due to private interest in my spare time. There is no contract forcing me to do it.

 

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Patryk F

It is sad but true that I must agree with Griga's last post.

 

Although My request for that would be second on the list, we are still  in the minority, and that is why I understand Griga's point absolutely.

On the other hand however,  if we can find an out of the box solution for supporting this type of AD,  that might eventually increase a number of licensed users, thus may increase the income.

Of course, we have no guarantee that it will actually happen.

Moving forward to the more pleasant, technical side, I have checked the VLC trick (at least on a ts file) and it of course works :-).

anyway, it is worth checking the document attached above since it includes nearly all variants of AD that may be embedded into the TS.

In my opinion: if it is possible, I would appreciate the Receiver mix support in the future anyway.

It is simply a matter of convenience and simplicity.

While we are technical geeks and the vlc trick seems relatively easy, it might be not that easy for one without the appropriate knowledge of configuring all that stuff.

 

It does not have to be a priority, dedicated feature.

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Griga

There won't be a pure DVBViewer based solution. Modifying the playback system for mixing audio tracks is very expensive. With other words, the cost-value ratio is very bad. If you count on it, you will wait forever.

 

On the other side, there are several options for Media Server based solutions. Partly they already work without any changes.

 

The DVBViewer Media Server provides DVBViewer capabilities in its web interface, which means, there is a kind of web site in your browser that provides your channel list, EPG, a list of your recordings and other media files etc. Of course you can schedule, start and stop recordings. And you can even play TV or files in your browser.

 

Since browsers are not able to play DVB formats, the Media Server must transcode video and audio to another format before delivering it. It uses FFmpeg for this task. FFmpeg is an extremely powerful freeware tool, called "the swiss army knife of media conversion". One can do almost everything with it. I'm sure that it can be configured to mix audio tracks. This means, most likely it will be possible to provide a receiver mix solution if TV or files delivered by the Media Server are played in the browser. Of course you may also use other clients for playing these transcoded streams. For example DVBViewer. It allows to store the stream addresses (URLs) as channel list entries.

 

By the way: A big advantage of the Media Server is that it can be used on remote computers, which means on all PCs and mobile devices in your home network. You are not glued anymore to the PC where your DVB stuff is installed. Some people even use it over the internet, e.g. for checking recordings when they are out at work.

 

Another option that uses the Media Server and the VLC playback engine is UPnP (Universal Plug and Play). The Media Server is a UPnP server. VLC is a UPnP client. That means, the VLC lists all media provided by the server in a kind of tree structure. You can select TV and radio channels, recordings and media files there, and the VLC will play it quite happily, of course with mixed audio tracks, if it is launched with the command line mentioned above. This already works - I've just tried it.

 

The third option is a playlist download. The Media Server web interface allows to download the channel list or parts of it or a list of recordings etc. as playlist in M3U format. Usually the browser opens a download dialog in this case, asking what it shall do with it. You can save it somewhere on disk or pass it directly to an application that shall handle it. I've just tried to let Firefox pass it to a VLC batch file with the following content (please note %1 at the end of the line).

 

start "" "C:\Program Files (x86)\VideoLAN\VLC\vlc.exe" --sout-all --sout #display %1

 

It works well. VLC opens the playlist, displays it, so you can select the contained elements and immediately starts to play the first one. Of course with mixed audio tracks.

 

Now some words about unwanted audio tracks in the mix. They can be excluded in the VLC Audio Track menu. However, it may be a bit cumbersome to do it again and again. This can be solved in DVBViewer. Since the Media Server does not provide a channel editor and scanner, DVBViewer has to be used to configure the server's channel list and favourites list. It is possible to delete the unwanted audio tracks and tick the "Don't update automatically" checkbox in the channel editor. This prevents DVBViewer and the Media Server from automatically adding other audio tracks again. However, this option entails disadvantages, so it may be worth looking for a better solution.

 

This is my concept so far. An open question is the accessibility of the web interface and the Media Server in general for blind people, due to lack of experience. I don't know if there are already blind people using it. Maybe some enhancements are required. This would depend on your feedback.

 

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Patryk F

 

Yes, I might try that solution :) 

Testing the accessibility and usability features from the blind perspective is a good argument to enhance my currently used license by a media server

I am an user since the DVBVserver.exe file was attached to the viewer, so very long ago.

Setting only the usable tracks in the channel is of course a way to go, but i never thought this way, since I prefer to have all the tracks as intended by the broadcaster :-)

 

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userip

Hi,

 

I feel this suggestion is great!
And I suggest to implement too a KEY to change the audio track in the preview window of the TransEdit. At time it's impossible to change from one audio track to another. I use this tool a lot, and this missing function complicates the use. This will help also to impaired people.

 

Thank you!

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Roberto Lombino

Thanks very much for all your suggestions. The solution I use is as follows:
1. I downloaded the RTSP channel list from the media server.
2. If I launch it in VLC with the parameter mentioned above (using a bat file), I can play more tracks at one time.
3. The list of playlist items can be reached with the key shortcut CTRL+L in VLC and then pressing Tab.
4. Strangely, VLC plays all audio tracks of a channel by default with this parameter, except for the AD track. So if the channel contains more tracks, I have to switch them off, then I select the main track and then the description.
One of the main reasons why I asked about the Czech AD was to find a solution for other blind persons from my country and Slovakia, where the same system is used. Unfortunately, it’s a bit complicated, but apparently this is the only solution.

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userip
On 12/2/2018 at 7:27 PM, Roberto Lombino said:

Thanks very much for all your suggestions. The solution I use is as follows:
1. I downloaded the RTSP channel list from the media server.
...

Thank you, Roberto!

 

My request is because I use a lot the TransEdit tool. I purchase the DVBViewer because this tool. So, for this reason I can't "download the RTSP channel list". I use physical SAT>IP servers.

 

In any case, I hope the developers of this great tool (TransEdit) will consider to continue developing it. At least for users who have paid for it.

Regards.

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