[vlc-devel] [PATCH 1/2] share: add wrapper script for the YoutubeDL Python module

[Steve Lhomme]

On 2020-09-21 10:30, Marvin Scholz wrote:
> 
> 
> On 21 Sep 2020, at 10:22, Steve Lhomme wrote:
> 
>> On 2020-09-20 20:57, Rémi Denis-Courmont wrote:
>>> This script generates a M3U playlist from a given URL, providing a
>>> simple serial format that can be read and parsed by another process.
>>>
>>> There are in principles two other alternative ways to access it:
>>>
>>> 1) Calling the YoutubeDL module directly in-process through CPython.
>>>     This poses a number of problems:
>>>     - CPython must be loaded by the main executable. Python modules will
>>>       fail to resolve their CPython symbols otherwise.
>>>     - Multiple CPython interpreters are still very immature; GIL behaves
>>>       weirdly. CPython is really not meant for multithread.
>>>     - The GIL prevents concurrent uses (that's the whole point of it).
>>>     - CPython network I/O cannot be interrupted by VLC interruptions, so
>>>       the calling thread may get stuck inside CPython.
>>>     - A build-time dependency on CPython is added.
>>>
>>> 2) Parsing the output of the youtube-dl program. This is what MPV does.
>>>     But this requires a whole new parser for the Python syntax.
>>>
>>> With a custom Python script, we can decide on the serialisation format
>>> that most suits the usage.
>>> ---
>>>   share/Makefile.am     |   2 +
>>>   share/ytdl-extract.py | 103 ++++++++++++++++++++++++++++++++++++++++++
>>>   2 files changed, 105 insertions(+)
>>>   create mode 100755 share/ytdl-extract.py
>>>
>>> diff --git a/share/Makefile.am b/share/Makefile.am
>>> index 2373ffbe91..8a92f04360 100644
>>> --- a/share/Makefile.am
>>> +++ b/share/Makefile.am
>>> @@ -49,6 +49,8 @@ nobase_dist_pkgdata_SCRIPTS = \
>>>       utils/audio-vlc-default.sh \
>>>       utils/video-vlc-default.sh \
>>>       $(NULL)
>>> +
>>> +dist_pkgdata_SCRIPTS = ytdl-extract.py
>>>   endif
>>>    EXTRA_DIST += \
>>> diff --git a/share/ytdl-extract.py b/share/ytdl-extract.py
>>> new file mode 100755
>>> index 0000000000..2d784c5090
>>> --- /dev/null
>>> +++ b/share/ytdl-extract.py
>>> @@ -0,0 +1,103 @@
>>> +#! /usr/bin/python3
>>> +#
>>> +# Copyright (C) 2020 Rémi Denis-Courmont
>>> +#
>>> +# This program is free software; you can redistribute it and/or 
>>> modify it
>>> +# under the terms of the GNU Lesser General Public License as 
>>> published by
>>> +# the Free Software Foundation; either version 2.1 of the License, or
>>> +# (at your option) any later version.
>>> +#
>>> +# This program is distributed in the hope that it will be useful,
>>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>> +# GNU Lesser General Public License for more details.
>>> +#
>>> +# You should have received a copy of the GNU Lesser General Public 
>>> License
>>> +# along with this program; if not, write to the Free Software 
>>> Foundation,
>>> +# Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
>>> +
>>> +import sys
>>> +import youtube_dl
>>
>> How does this work if the import library is not there ? Do we have 
>> requirements on the version of the library ? Can we check it in 
>> configure.ac ?
> 
> Checking it in configure.ac seems useless as this is about the host 
> system, not a build time requirement.
> If the library is not there or its the wrong version so API does not 
> match, it the script would just fail
> which IIUC is handled properly by the access module calling the script.
> 
>> Can it be part of contribs ?
> 
> Could be possible, but IMO out of scope of this patchset.
> 
>> Should we run python with out local environment with our little set of 
>> dependencies ?
> 
> Why would you want to do that? I dont really see any benefit doing so 
> while possibly
> breaking the import.

I think it's the opposite. Using the system dependencies might be the 
one breaking the version we support.