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

[Marvin Scholz]

On 21 Sep 2020, at 10:51, Steve Lhomme wrote:

> 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 ?

Ok, I dont understand what you mean by that then, sorry.

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