[vlc-devel] [PATCH] [RFC] add demux filters that are similar in API to regular demuxers

[Rémi Denis-Courmont]

Le 2016-06-06 11:11, Steve Lhomme a écrit :
> On Sun, Jun 5, 2016 at 2:15 PM, Rémi Denis-Courmont <remi at remlab.net> 
> wrote:
>> Le 2016-06-05 13:03, Steve Lhomme a écrit :
>>>
>>> The only difference is that when control/demux callbacks are 
>>> called, they
>>> are
>>> given the next demuxers to call in the chain
>>>
>>> --
>>> replaces https://patches.videolan.org/patch/13585/
>>> and https://patches.videolan.org/patch/13615/ with legacy patch 
>>> remaining
>>> I do not understand how some demuxers have pf_demux to NULL, so 
>>> there
>>> might be
>>> some simplifications possible.
>>> ---
>>>  NEWS                  |   3 ++
>>>  include/vlc_demux.h   |  12 ++++++
>>>  src/input/demux.c     | 106
>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  src/input/demux.h     |   3 ++
>>>  src/input/input.c     |   9 +++++
>>>  src/input/var.c       |   1 +
>>>  src/libvlc-module.c   |   5 +++
>>>  src/playlist/engine.c |   1 +
>>>  8 files changed, 140 insertions(+)
>>>
>>> diff --git a/NEWS b/NEWS
>>> index fd5e690..b6eeb06 100644
>>> --- a/NEWS
>>> +++ b/NEWS
>>> @@ -101,6 +101,9 @@ Stream filter:
>>>   * Added stream prebuffering plugin
>>>   * Removed HTTP Live streaming stream filter
>>>   * Added zlib (a.k.a. deflate) decompression filter
>>> +
>>> +Demux filter:
>>> + * Added a demuxer filter chain to filter or intercept control
>>> commands and demuxing
>>>
>>>  Audio output:
>>>   * Complete rewrite of the AudioTrack Android module. This is now
>>> the default.
>>> diff --git a/include/vlc_demux.h b/include/vlc_demux.h
>>> index 1153e1c..0c4bfeb 100644
>>> --- a/include/vlc_demux.h
>>> +++ b/include/vlc_demux.h
>>> @@ -77,16 +77,25 @@ struct demux_t
>>>
>>>      /* Weak link to parent input */
>>>      input_thread_t *p_input;
>>> +
>>> +    /* demux_t filter chaining */
>>> +    demux_t        *p_next;
>>> +    demux_t        *p_prev;
>>
>>
>> Should not be needed.
>
> For now when a demuxer changes the info values, it calls the previous
> demux in line to inform it.

No. For the last time, you cannot do that. It violates the memory model 
given that the demux_t "interface" is not expected or designed to be 
reentrant. More accurately, you cannot ensure that it will not violate 
the memory model (not that the subtlety matters much).

-- 
Rémi Denis-Courmont
http://www.remlab.net/