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

[Steve Lhomme]

On 2020-09-21 10:39, Marvin Scholz wrote:
> 
> 
> On 21 Sep 2020, at 10:38, Steve Lhomme wrote:
> 
>> On 2020-09-21 10:36, Marvin Scholz wrote:
>>>
>>>
>>> On 21 Sep 2020, at 10:34, Steve Lhomme wrote:
>>>
>>>> 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.
>>>
>>> Not sure what you mean by "version we support" as we rely on the 
>>> system-installed
>>> youtube-dl here. Worst case the API is different and it fails?
>>
>> If the youtube-dl of the system changes with a different API or way or 
>> working that we support it breaks the feature in VLC. If we have our 
>> local version of youtube-dl we don't have this problem.
> 
> We don't have a "local" version of youtube-dl though

My question was:
Should we run python with out local environment with our little set of 
dependencies ?