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

[Marvin Scholz]

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

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