[Ohrrpgce] SDL_mixer and loop points

Thu Nov 21 17:27:07 PST 2019

Yes, that's the core difference between GPL and LGPL.

I was interested in it on Android for the MIDI synths. If we had a
OPL3-synth-based BAM player, we would ideally want to be able to use it
everywhere, including possibly GPL-problematic platforms. However I'd think
no one is going to be using BAM files in a Switch or Steam game, so such a
restriction would be bearable.
On the other hand there are non-GPL OPL3 synths we could use instead for
BAM: https://doomwiki.org/wiki/OPL_emulation#OPL_emulators
And, I still think implementing a BAM player is a quite bad use of time.
It's only for fun.

On Fri, 22 Nov 2019 at 13:35, James Paige <Bob at hamsterrepublic.com> wrote:

> I must have been confusing the LGPL rules.
>
> What was the reason for wanting SDL Mixer X on Android, just for the
> Midi/BAM synths?
>
> On Thu, Nov 21, 2019, 6:57 PM Ralph Versteegen <teeemcee at gmail.com> wrote:
>
>> You can't dynamically link to a GPL library without the whole program
>> being GPL.
>>
>> I haven't forgotten about the relicensing either, I need to send that
>> email.
>>
>> It would be rare that someone would be using a backend without loop point
>> support (eg non-MIDI audio don't even work in music_native/native2 on
>> Windows currently; noone is using them), but that warning would be a good
>> idea.
>>
>> On Fri, 22 Nov 2019 at 01:53, James Paige <Bob at hamsterrepublic.com>
>> wrote:
>>
>>> The loop support thing sounds cool. I like the idea of in editor
>>> support, although we'll probably also want some in-editor warning text to
>>> let people know that support is dependent on backend.
>>>
>>> As for the relicensing, I haven't forgotten about that. I do still want
>>> to do it.
>>>
>>> Could using a GPL3 licenced music library work better if it was a
>>> dynamic library, for greater separation? Sort of like how gfx_directx is
>>> implemented as a dll?
>>>
>>> ---
>>> James
>>>
>>> On Thu, Nov 21, 2019, 6:33 AM Ralph Versteegen <teeemcee at gmail.com>
>>> wrote:
>>>
>>>> I know I've discussed this before, but apparently not on the
>>>> mailinglist.
>>>>
>>>> SDL_Mixer 2 added support for .ogg loop points a couple of years ago.
>>>> (Strangely it's not in the changelog)
>>>>
>>>> Loop points work as LOOPSTART and LOOPEND or LOOPLENGTH (optional)
>>>> comments embedded in the .ogg file. LOOPSTART+LOOPLENGTH is RPG
>>>> Maker-compatible.
>>>>
>>>> Within the last few days to weeks, more stuff has landed in SDL_mixer
>>>> hg.
>>>> -loop points in FLAC files (note: I compiled sdl_mixer.dll without FLAC
>>>> support)
>>>> -loop points can now be expressed in hh:mm:ss notation, or named
>>>> LOOP_START or LOOP-START, for compatibility with Doom source ports
>>>> https://zdoom.org/wiki/Audio_loop
>>>> -loop points now respect the number of times we asked SDL_mixer to loop
>>>> the song. I believe after that number of loops, it'll proceed past LOOPEND
>>>> to the end, and then stop (not loop to beginning). Someone could always
>>>> submit a patch for another comment controlling a separate loop count.
>>>>
>>>> So I would like to add the ability to edit loop-points right in the
>>>> music import menu.
>>>>
>>>> We already have code for adding comments to an .ogg file when
>>>> converting .mp3 to .ogg, but it seems to oggenc can't be used to add
>>>> comments to an existing ogg file. Instead, the vorbiscomment program (part
>>>> of vorbis-tools) does that. Another 186kB download.
>>>> <http://www.rarewares.org/files/ogg/vorbiscomment-1.2.0.zip>
>>>>
>>>> === SDL_mixer 1.2 ===
>>>>
>>>> Loop points aren't in SDL_mixer 1.2. There hasn't been an update to
>>>> SDL_mixer 1.2 since 2012, but it looks like they're preparing a bugfix one,
>>>> including a number of backported loop-related bugfixes. It's certainly not
>>>> getting any features.
>>>>
>>>> There are only a couple bugs that I'm aware of left in gfx_sdl2; I'd
>>>> like to fix them and switch to it as default on Mac, Linux and Windows
>>>> after Fufluns is released
>>>>
>>>> However the ogg loop stuff is spread over just a few of commits and
>>>> should be very easy to backport to SDL_mixer 1.2, for our own build of
>>>> sdl_mixer.dll (for people who want to stick to gfx_sdl instead of gfx_sdl2
>>>> for whatever reason) and also for the android port.
>>>>
>>>> === SDL_mixer X ===
>>>>
>>>> Loop points were first implemented in SDL_mixer X, which is a fork of
>>>> SDL_mixer 2, which has a number of interesting features.
>>>> https://wohlsoft.github.io/SDL-Mixer-X/
>>>>
>>>> Most notably, it supports many more module formats and has ADLMIDI
>>>> (OPL3) and OPNMIDI OPN2 synthesizer-based MIDI players, which could be used
>>>> to play MIDI on Android or elsewhere without needing soundfonts. Sounds
>>>> different to MIDI playback with a soundfont, but I think in most case
>>>> ADLMIDI not bad (except percussion maybe). These both also support
>>>> controller 111-based loop points (RPG Maker-compatible), just like
>>>> music_native/native2 do. They could also be used to implement true BAM
>>>> playback. (ADLMIDI contains at least two OPL3 synthesizers: Nuked and
>>>> DOSbox)
>>>>
>>>> But these synths are GPLv3+ licensed, which is a problem (inhibiting
>>>> relicensing of the engine). So maybe we could use it just on Android for
>>>> MIDI playback, and not for BAM. iOS has MIDI support builtin.
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