An audio mixer that supports various file formats for Simple Directmedia Layer.

• Keeps the original stb_vorbis as intact as possible so that future updates from mainstream would be painless.
• Reduces STB_VORBIS_MAX_CHANNELS from 16 to 6 (objections?)
• Adds several missing libm function overrides,
• SDL_mixer now requires SDL >= 2.0.9 because of SDL_exp()
• Fixes slow loads and leaks in start_decoder: https://github.com/nothings/stb/pull/1174
• Fixes submap array out-of-bounds indexing bug: https://github.com/nothings/stb/pull/1312
• Replace signed overflow clamps with unsigned overflow: https://github.com/nothings/stb/issues/1168
• Replaces alloca() usage with setup_malloc() (from libxmp.)
• Fixes '-Wmaybe-uninitialized' warnings in get_seek_page_info: https://github.com/nothings/stb/pull/1172
• A minor UBSan fix and suppression: https://github.com/nothings/stb/issues/1168
• Fixes signature of dummy realloc() for STB_VORBIS_NO_CRT: https://github.com/nothings/stb/pull/1198
• Renames BUFFER_SIZE macro to STB_BUFFER_SIZE: https://github.com/nothings/stb/pull/1078
• Pulls in sample-accurate offset patch of Vitaly Novichkov: (stb_vorbis_get_playback_sample_offset, because it's used in OGG_Tell and OGG_GetSome): https://github.com/nothings/stb/issues/1294 https://github.com/nothings/stb/pull/1295
• Fixes a few warnings here and there in some environments.
• Replaces two dummy '(void) 0' with 'do {} while(0)'

There's some background on this issue in the rust-sdl2 project. It seems that on the Mac while Wave files work happily if mixer is unload before the music file is but Opus causes a SEGFAULT.

Digging deeper, it turns out that there isn't a proper guard in OPUS_Delete to make sure that the Opus library is still loaded.

The fix seems to be to make sure "opus.loaded" is greater than zero before calling opus.op_free().

Does this seem reasonable? Also, I noticed that you can leak the Opus libraries if calling OPUS_Load() more than once.

If this does make sense, I'm happy to write a merge request here. It seems like @Wohlstand would be a good mentor for this if they're willing to help me out.

Hi all,

This is essentially the same as my issue for SDL_image (https://github.com/libsdl-org/SDL_image/issues/288). Basically, native MIDI as well as decoders for Modplug and Opus have been removed from the official macOS binaries, while they are all still enabled/included (albeit in an "optional" folder) for the Windows binaries.

I understand making various dependency libraries optional, but is there a way to have pre-built optional dependencies included for the macOS release, the same way they are for Windows? A folder of pre-built frameworks that can be dragged inside the mixer framework or into the same folder as the framework?

Thanks in advance!

Austin

• Make the master_volume variable being atomic
• Fixed the master_volume behavior at the music (there a middle buffer should be allocated to safely apply the volume effect)

Bonus: whitespace clean-up at the mixer.c.

As far as I can tell, the last release was 2018 and there have been > 300 commits since then. Any chance for a new release? Or perhaps there are blockers for that?

Resolves #334

An argument of property in Timidity config can be surrounded with " or ' characters to prevent splitting into several arguments if it contains spaces or other delimiter characters.

If an argument itself contains " characters it should be surrounded with ' characters and vice versa.

In order to support static linking, SDL_mixer.pc should include a 'Libs.private' field listing all the libraries that SDL_mixer requires.

This patch adds such a field and also modifies configure.ac so that EXTRA_LDFLAGS (which is now also used as the value of 'Libs.private') no longer includes SDL_LIBS. This is done so as to prevent libraries required by SDL from being listed twice when 'pkg-config --libs --static SDL_mixer' is run (they're already shown because of the 'Requires: sdl' line in SDL_mixer.pc). Makefile.in is also adjusted accordingly.

Upstream status: submitted https://bugzilla.libsdl.org/show_bug.cgi?id=3278

Signed-off-by: Rodrigo Rebello [email protected] [Retrieved from: https://git.buildroot.net/buildroot/tree/package/sdl_mixer/0001-Add-Libs.private-field-to-pkg-config-file.patch] Signed-off-by: Fabrice Fontaine [email protected]

due to the compiler option /MD and the use of memcpy and memset, including SDL2_mixer.dll will create a dependency on the visual studio run time DLLs, which isn't desirable. Either use SDL_memset / SDL_memcpy or /MT instead of /MD.

One mp3 I have reports 56.607347s duration instead of about 31.320816s with libmad backend: I can attach the mp3 in question here.

Originally posted in https://github.com/libsdl-org/SDL_mixer/issues/300#issuecomment-1140079544

In some cases we need to set the overall volume level. For now we have only two ways:

• modify chunk's volume
• modify channel's volume

Both are bad in case when we need to modify all played now sounds and all sounds that will be played in the future. To solve this problem I suggest new function Mix_MasterVolume(int) which works with single static variable int master_volume. This variable is used in mix_channels/music_mixer to calculate current volume level.

Addition to https://github.com/libsdl-org/SDL_mixer/commit/143b0bbfd50654af667c87143c1a2d69ef80f151

EDIT: As was discussed below, I changed the entire goal of this PR:

C standard gives guarantee they will be NULLed by default: https://port70.net/~nsz/c/c89/c89-draft.html#3.5.7

If an object that has static storage duration is not initialized explicitly, it is initialized implicitly as if every member that has arithmetic type were assigned 0 and every member that has pointer type were assigned a null pointer constant. If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate.

I'm running SDL 2.0.22 and SDL_mixer 2.60 on macOS 12.5.

I'm attempting to open an audio device as follows, after calling SDL_Init (audio and video), and Mix_Init:

Mix_OpenAudio(
    MIX_DEFAULT_FREQUENCY,
    MIX_DEFAULT_FORMAT,
    MIX_DEFAULT_CHANNELS,
    2048
)

The error I get is as follows:

MEMixerChannel.cpp:1636  client <[email protected]; [0]; play> got error 2003332927 while sending format information

I'm also having the same issue calling Mix_CloseAudio()

This is potentially useful to allow building with libvorbis, libFLAC and libmpg123 for the reasons described in https://github.com/libsdl-org/SDL_mixer/issues/427#issuecomment-1186630491, while still having the internal libraries as fallbacks if dynamic loading fails.

TODO:

• Additional CMake changes to allow enabling both libvorbis and stb_vorbis
• Should libvorbis, libFLAC and libmpg123 be enabled by default?

Thank you for this great library. I've integrated it into my project over the last few days and it's working very well. However, I have a suggestion for improvement in regard to the volume controls. SDL currently implements audio volume control as a simple linear attenuation of the input signal. The problem with this is that it's not an accurate model of how hearing works.

Due to the characteristics of the human ear, there is a logarithmic relationship between the amplitude of an audio signal and its perceived loudness, which is why loudness is typically measured in decibels. The linear scale results in an extremely uneven distribution of loudness. This can be demonstrated with a simple SDL_mixer test program: play a chunk sound effect at MIX_MAX_VOLUME (128), then change the channel volume to half (64) and recompile and play again. You will notice that there is only a very slight reduction in the loudness, despite the volume being halved. Indeed, halving the amplitude of an audio signal reduces its loudness by only 6 dB. The difference is even more apparent when comparing the top 25% and bottom 25% of the scale. The difference between 128 and 96 is only 2.5 dB, but the difference between 35 and 1 is more than 30 dB.

My Implementation

I would like for the users of my application to be able to specify channel volume on a limited scale that is linear with respect to loudness instead of signal amplitude. I designed a wrapper function for Mix_Volume() to convert the requested application-level log volume to the internal SDL linear attenuation factor volume.

There are a couple factors that go into designing a log scale volume control. The first is the dynamic range in dB, which is the volume difference between the loudest signal and the quietest. Since we have 128 volume steps in SDL, the most we can attenuate the signal is 1/128, which is about -42 dB. I rounded this to -40 dB.

Next is the number of volume steps. Ideally, I would like to have a volume scale of 0-100. Unfortunately, with a limited resolution of only 128 steps in SDL, a 0-100 scale cannot produce a unique SDL volume for each step due to rounding, so I decided to settle for a simpler 0-10 scale. In this scale, a value of 10 corresponds to 0 dB (full, unattenuated signal), while 0 corresponds to -40 dB. However, I decided to set 0 to a volume of 0, since most users will interpret 0 as meaning complete silence. Each step in the scale corresponds to a 4 dB adjustment, plus or minus a bit due to rounding. I created a spreadsheet with the calculations which is screenshotted below:

Here is how I chose to implement this volume control in C++. Since the log and power functions can be computationally expensive, I pre-calculate the SDL volume values at compile time for each step in the scale using a constexpr lambda function, and store the results in a static array. Then, determining the SDL volume at runtime is simply accessing the array at the requested volume step.

I chose to use constexpr lambda strictly for convenience purposes, so I could alter the macro values and recompile without having to manually type the array values from the spreadsheet each time. But this function could be easily adapted to C by doing that instead of the lambda.

#define MAX_VOLUME 10
#define RANGE_DB -40

int Sound::set_volume(int channel, int volume)
{
    if (volume > MAX_VOLUME || volume < 0)
        return 1;

    constexpr auto generate_array = []() {
        double a = pow(10.f, (double) RANGE_DB / 20.f);
        double b = log10(1.f / a) / (double) MAX_VOLUME;
        std::array<int, MAX_VOLUME + 1> arr;
        arr[0] = 0;
        arr[MAX_VOLUME] = MIX_MAX_VOLUME;
        for (int n = 1; n < MAX_VOLUME; n++) {
            arr[n] = (int) std::round(a * pow(10.f, (double) n * b) * (double) MIX_MAX_VOLUME);
        }
        return arr;
    };
    static constexpr std::array<int, MAX_VOLUME + 1> volume_array = generate_array();
    
    Mix_Volume(channel, volume_array[volume]);
    return 0;
}

I don't support the volume querying here because I don't personally need it, but it would be trivial to implement.

Proposal

My proposal is to add a logarithmic volume control function with a title such as Mix_VolumeLog() or Mix_VolumeDB(), which would be implemented similar to the above. The fundamentals of psychoacoustics are not well understood by many people, so I believe it would provide a very useful abstraction for implementing application-level volume control. Since it uses SDL's current volume controls underneath, it would not break any existing functionality nor the ABI.

We got a request that our downstream package should be built with the new dr_ stb_ internal decoders instead of the external libraries such as libvorbis/libflac/mpg123.

What's the recommended way to build sdl_mixer for downstream distributions?

thanks!

The current CI fails because libxmp is missing vendored library CMake support: https://github.com/libsdl-org/SDL_mixer/runs/7365768492?check_suite_focus=true

Maybe we don't need it? It's provided for Visual Studio in VisualC/external

What's the best way to fix this?

This call allows cheaper pausing/resuming of the whole audio processing without pausing every playing channel or music stream.

For example, this call can be used to pause the entire audio playback when the game is not focused.

Note: the "pause_async_music" call is required for music which is playing asynchronously from the main audio output processor, for example, OS Native MIDI. However, the stuff doesn't affect CMD Music which will still play (however, never tested this as I never used CMD music for my needs).