RFC: dvbzap application based on DVBv5 API

RFC: dvbzap application based on DVBv5 API

[Mauro Carvalho Chehab]

In order to test the large chunk of patches I've made those days, I wrote
a dvbzap application using DVBv5 API, based on tzap.

It is at my experimental v4l-utils tree, at branch dvb-utils:
	http://git.linuxtv.org/mchehab/experimental-v4l-utils.git/shortlog/refs/heads/dvb-utils

in order to test, please use:
	git clone git://linuxtv.org/mchehab/experimental-v4l-utils.git

While I tested it only with ISDB-T, it will likely work with DVB-T, ATSC and DVB-C,
if CA is not needed.

TODO:
- Add proper support for Satellite delivery systems. It will likely
  recognize a DVB-S zap file, but it won't work, as polarization setting were not
  implemented, nor any DISEqC commands;
- Add support for CA;
- Be more flexible with regards to the channels.conf files.

One of the changes I'm experimenting with this tool is to define a new format to
show DVBv5 channels/transponders.

As you likely know, the current formats on the existing DVBv3 tools are 
standard-dependent. Even the existing DVBv5 applications I'm aware of currently
write the channels file on a DVBv3, due to compatibility issues.

So, a new format for channels is needed.

The current code has one function to write on a new format. I lacks a parser for it
(it shouldn't be hard to write one - a few hours should be enough for doing that).

The format I'm thinking is to use:

[channel name]
	property = value
...
	property = value

This allows the same format to be used by any DVBv5 supported delivery system. 
It will even allow to mix channels from different delivery systems on the same file.
This could be useful for devices like DRX-K, that supports multiple delivery
systems with different parameters.

As an example, this is what it produces from a DVB-T zap file:

[TV Brasil SD]
        VIDEO_PID = 769
        AUDIO_PID = 513
        SERVICE_ID = 16161
        DELIVERY_SYSTEM = DVBT
        FREQUENCY = 479142857
        INVERSION = AUTO
        BANDWIDTH_HZ = 6000000
        CODE_RATE_HP = AUTO
        CODE_RATE_LP = AUTO
        MODULATION = QAM/AUTO
        TRANSMISSION_MODE = AUTO
        GUARD_INTERVAL = AUTO
        HIERARCHY = NONE

The same entry without audio/video/service ID's (like the ones used 
by scan) would look like:

[CHANNEL]
        DELIVERY_SYSTEM = DVBT
        FREQUENCY = 479142857
        INVERSION = AUTO
        BANDWIDTH_HZ = 6000000
        CODE_RATE_HP = AUTO
        CODE_RATE_LP = AUTO
        MODULATION = QAM/AUTO
        TRANSMISSION_MODE = AUTO
        GUARD_INTERVAL = AUTO
        HIERARCHY = NONE

My next steps with regards to this tool are to:

1) convert a scan tool to use the same libraries as dvbzap is
   using, in order to generate an output file for scan with the same format;

2) to implement a parser for the new format (this should be easy, so maybe
   I'll start with this).

Comments, ideas, patches, etc are welcome.

Regards,
Mauro

Re: RFC: dvbzap application based on DVBv5 API

[Akihiro TSUKADA]

> [channel name]
> 	property = value
> ...
> 	property = value

Currently, at least gstreamer's dvbbasebin and mplayer assumue that
the channel configuration file has the format of one line per channel.
So when I personally patched them to use v5 parameters,
I chose the one-line-per-channel format of
  <channel name>:propname=val|...|propname=val:<service id>, for example,
 NHKBS1:DTV_DELIVERY_SYSTEM=SYS_ISDBS|DTV_VOLTAGE=1|DTV_FREQUENCY=1318000|DTV_ISDBS_TS_ID=0x40f2:103
, to minimize modification (hopefully).
I understand that it is not that difficult nor complicated 
to adapt applications to use the ini file style format,
but the old one line style format seems slightly easier.

and I wish that the channel configuration can allow nicknames/aliases,
as the canonical channel name can be long to type in or difficult to remember correctly.
If I remember right, MythTV has its own database,
and it would be convenient if we could share the database,
because applications currently have their own channel configuration separately,
and the configuration change like new service or parameter changes must be
propagated manually.

regards,
Akihiro

Re: RFC: dvbzap application based on DVBv5 API

[Mauro Carvalho Chehab]

Hi Akihiro,

On 30-12-2011 04:46, Akihiro TSUKADA wrote:
>> [channel name]
>> 	property = value
>> ...
>> 	property = value
> 
> Currently, at least gstreamer's dvbbasebin and mplayer assumue that
> the channel configuration file has the format of one line per channel.
> So when I personally patched them to use v5 parameters,
> I chose the one-line-per-channel format of
>   <channel name>:propname=val|...|propname=val:<service id>, for example,
>  NHKBS1:DTV_DELIVERY_SYSTEM=SYS_ISDBS|DTV_VOLTAGE=1|DTV_FREQUENCY=1318000|DTV_ISDBS_TS_ID=0x40f2:103
> , to minimize modification (hopefully).
> I understand that it is not that difficult nor complicated 
> to adapt applications to use the ini file style format,
> but the old one line style format seems slightly easier.

It is not that harder to parse a multiple lines file, but using something like above
makes harder for humans to read. Also, the format I've proposed is already handled
by several existing tools. So, there are several parsers for it already
written.

> and I wish that the channel configuration can allow nicknames/aliases,
> as the canonical channel name can be long to type in or difficult to remember correctly.
> If I remember right, MythTV has its own database,
> and it would be convenient if we could share the database,
> because applications currently have their own channel configuration separately,
> and the configuration change like new service or parameter changes must be
> propagated manually.

Yes, this is an interesting feature. Some carriers broadcast nicks/aliases via
the emphasis encoding. It shouldn't be hard to add support for it.

Btw, I finished writing a dvbv5-scan application. It reads (currently) the 
legacy channels/transponders format found on dvb-apps, and outputs channel
scans on the new format.

I decided to write the scan tool from scratch, instead of importing the code from
w_scan or dvb-apps/scan, as it allowed me to avoid importing DVBv3 legacy stuff
on it, and to separate the scan code into a few function calls.

Due to that, only a subset of the features found on the other scan tools are there
(the ones that are needed for ISDB-T - and - likely DVB-T). I'm currently without
DVB-C signal, but, as soon as I return back to my hometown, I'll add the missing
bits for it.

I also wrote a small utility to convert from the legacy zap and channels.conf
formats into the new one. It is at:

	http://git.linuxtv.org/mchehab/experimental-v4l-utils.git/shortlog/refs/heads/dvb-utils


Of course, patches, help, etc are welcome!

Regards,
Mauro