demux: add a POS

I regret doing this so much, it's fucking garbage.

Fixes: #5100

demux/demux.c

@@ -66,6 +66,7 @@ extern const demuxer_desc_t demuxer_desc_rar;
 extern const demuxer_desc_t demuxer_desc_libarchive;
 extern const demuxer_desc_t demuxer_desc_null;
 extern const demuxer_desc_t demuxer_desc_timeline;
+extern const demuxer_desc_t demuxer_desc_midi;
 
 static const demuxer_desc_t *const demuxer_list[] = {
     &demuxer_desc_disc,
@@ -78,6 +79,9 @@ static const demuxer_desc_t *const demuxer_list[] = {
     &demuxer_desc_libarchive,
 #endif
     &demuxer_desc_lavf,
+#if HAVE_FLUIDSYNTH
+    &demuxer_desc_midi,
+#endif
     &demuxer_desc_mf,
     &demuxer_desc_playlist,
     &demuxer_desc_null,

demux/demux_midi.c

@@ -0,0 +1,180 @@
+#include <math.h>
+
+#include <fluidsynth.h>
+
+#include "codec_tags.h"
+#include "demux.h"
+#include "stream/stream.h"
+
+// Arbitrary.
+#define FRAME_SAMPLES 1024
+#define SAMPLERATE 48000
+
+struct priv {
+    struct sh_stream *sh;
+    fluid_settings_t *settings;
+    fluid_synth_t *synth;
+    fluid_player_t *player;
+    uint64_t samples;
+    struct demux_packet *first_pkt;
+};
+
+static bool check_midi(uint8_t *buf, int size)
+{
+    if (size < 4 + 4 + 6 + 4)
+        return false;
+    if (memcmp(buf, "MThd", 4))
+        return false;
+    if (buf[4] || buf[5] || buf[6] || buf[7] != 6)
+        return false; // length must always be 6
+    if (buf[8] || buf[9] > 2)
+        return false; // version is always 0/1/2
+    if (memcmp(&buf[4 + 4 + 6], "MTrk", 4))
+        return false; // expect a MTrk chunk to follow
+    // Regarding bit 15 (SMPTE format flag): fluidsynth doesn't support it
+    int division = (buf[12] << 8) | buf[13];
+    return division > 0 && !(division & (1 << 15));
+}
+
+static bool d_read_packet(struct demuxer *demuxer, struct demux_packet **pkt)
+{
+    struct priv *p = demuxer->priv;
+
+    if (p->first_pkt) {
+        *pkt = p->first_pkt;
+        p->first_pkt = NULL;
+        return true;
+    }
+
+    if (fluid_player_get_status(p->player) != FLUID_PLAYER_PLAYING)
+        return false;
+
+    struct demux_packet *dp = new_demux_packet(FRAME_SAMPLES * 4 * 2);
+    if (!dp)
+        return true;
+
+    fluid_synth_write_float(p->synth, FRAME_SAMPLES,
+                            dp->buffer, 0, 2,
+                            dp->buffer, 1, 2);
+
+    dp->pts = p->samples / (double)p->sh->codec->samplerate;
+    p->samples += FRAME_SAMPLES;
+
+    dp->stream = p->sh->index;
+    dp->keyframe = true;
+    *pkt = dp;
+
+    return true;
+}
+
+static void d_close(struct demuxer *demuxer)
+{
+    struct priv *p = demuxer->priv;
+
+    if (p->player)
+        delete_fluid_player(p->player);
+    if (p->synth)
+        delete_fluid_synth(p->synth);
+    if (p->settings)
+        delete_fluid_settings(p->settings);
+    talloc_free(p->first_pkt);
+}
+
+static void no(int level, const char *message, void *data)
+{
+}
+
+static int try_open_file(struct demuxer *demuxer, enum demux_check check)
+{
+    struct priv *p = talloc_zero(demuxer, struct priv);
+    demuxer->priv = p;
+
+    uint8_t probe[STREAM_BUFFER_SIZE];
+    int len = stream_read_peek(demuxer->stream, probe, sizeof(probe));
+    if (len < 1 || !check_midi(probe, len))
+        return -1;
+
+    bstr data = stream_read_complete(demuxer->stream, demuxer, 1000000);
+    if (data.start == NULL)
+        return -1;
+
+    // Another idiot API with a global log callback and defaulting to stderr (or
+    // stdout on win32 - lol?). Shut it up to disable particularly stupid
+    // messages, such as about SDL (wtf? oh yes, they mess with SDL's fucking
+    // stupid global state too, even if you're not asking for it).
+    int fucking_stupid[] = {FLUID_PANIC, FLUID_ERR, FLUID_WARN, FLUID_INFO,
+                            FLUID_DBG};
+    for (int n = 0; n < MP_ARRAY_SIZE(fucking_stupid); n++)
+        fluid_set_log_function(fucking_stupid[n], no, NULL);
+
+    p->settings = new_fluid_settings();
+    if (!p->settings)
+        goto error;
+    if (fluid_settings_setstr(p->settings, "player.timing-source", "sample"))
+        goto error;
+    if (fluid_settings_setnum(p->settings, "synth.sample-rate", SAMPLERATE))
+        goto error;
+    p->synth = new_fluid_synth(p->settings);
+    if (!p->synth)
+        goto error;
+    p->player = new_fluid_player(p->synth);
+    if (!p->player)
+        goto error;
+
+    char *soundfont;
+    if (fluid_settings_dupstr(p->settings, "synth.default-soundfont", &soundfont))
+        soundfont = NULL;
+    if (!soundfont) {
+        MP_ERR(demuxer, "No sound font available.\n");
+        goto error;
+    }
+    int soundfont_st = fluid_synth_sfload(p->synth, soundfont, 1);
+    fluid_free(soundfont);
+    if (!soundfont_st) {
+        MP_ERR(demuxer, "Failed to load sound font available.\n");
+        goto error;
+    }
+
+    if (fluid_player_add_mem(p->player, data.start, data.len))
+        goto error;
+
+    p->sh = demux_alloc_sh_stream(STREAM_AUDIO);
+    struct mp_codec_params *c = p->sh->codec;
+    c->channels = (struct mp_chmap)MP_CHMAP_INIT_STEREO;
+    c->samplerate = SAMPLERATE;
+    c->native_tb_num = 1;
+    c->native_tb_den = c->samplerate;
+    mp_set_pcm_codec(p->sh->codec, true, true, 32, false);
+
+    demux_add_sh_stream(demuxer, p->sh);
+
+    if (fluid_player_play(p->player))
+        goto error;
+
+    // Fluidsynth has some sort of internal playlist, and it advances to the
+    // current one only if you "pull" some samples. That means we don't know
+    // whether the MIDI file can even be loaded by Fluidsynth until we read
+    // same data.
+    // This heuristic may fail on very short MIDI files.
+    d_read_packet(demuxer, &p->first_pkt);
+    if (fluid_player_get_status(p->player) != FLUID_PLAYER_PLAYING)
+        goto error;
+
+    talloc_free(data.start);
+    demuxer->seekable = false;
+    demux_close_stream(demuxer);
+
+    return 0;
+
+error:
+    MP_ERR(demuxer, "Fluidsynth failed to initialize.\n");
+    return -1;
+}
+
+const struct demuxer_desc demuxer_desc_midi = {
+    .name = "midi",
+    .desc = "MIDI via fluidsynth",
+    .open = try_open_file,
+    .close = d_close,
+    .read_packet = d_read_packet,
+};

wscript

@@ -383,6 +383,11 @@ iconv support use --disable-iconv.",
         'desc': 'SDL2 gamepad input',
         'deps': 'sdl2',
         'func': check_true,
+    }, {
+        'name': '--fluidsynth',
+        'desc': 'MIDI file playback support via fluidsynth',
+        'func': check_pkg_config('fluidsynth', '>= 2.1.5'),
+        'default': 'disable',
     }
 ]
 

wscript_build.py

@@ -276,6 +276,7 @@ def build(ctx):
         ( "demux/demux_lavf.c" ),
         ( "demux/demux_libarchive.c",            "libarchive" ),
         ( "demux/demux_mf.c" ),
+        ( "demux/demux_midi.c",                  "fluidsynth" ),
         ( "demux/demux_mkv.c" ),
         ( "demux/demux_mkv_timeline.c" ),
         ( "demux/demux_null.c" ),