Add built-in WebM movie player core (rwebm + rvp8/rvp9)

A dependency-free media player for WebM files, built entirely on
libretro-common: rwebm demuxes, rvp9 decodes VP9 and, when rvp8 is
present (HAVE_RWEBP), VP8.  Gated behind HAVE_WEBMPLAYER (default
off; requires HAVE_RWEBM and HAVE_RVP9, enforced by qb), it slots
into the existing built-in media player plumbing as the fallback
when neither FFmpeg nor MPV is compiled in -- consoles and other
minimal builds where those dependencies are unavailable.

The core handles VP9 superframes (invisible alt-ref frames packed
with the shown frame) and skips presentation of invisible VP8
frames via the frame-tag show bit while still feeding them to the
decoder for reference updates.  Output is XRGB8888 via BT.601
limited-range conversion; frame rate is derived from the shown
video packet count over the stream duration.  Audio tracks are
ignored for now (silence is output for pacing) pending an Opus
decoder in libretro-common.

Verified end-to-end: a standalone libretro harness drives the core
over nine VP8/VP9 streams (odd dimensions, real motion, alt-ref,
two-pass superframes) under AddressSanitizer with pixel-exact
output against libvpx-converted reference frames, and a full
RetroArch build (HAVE_WEBMPLAYER + null drivers) routes .webm
content to the core, plays it at the derived frame rate and shuts
down cleanly at end of stream.  A default build without the flag
is unaffected.

Author: LibretroAdmin

Makefile.common

@@ -2320,6 +2320,11 @@ ifeq ($(HAVE_RVP9), 1)
    OBJ += $(LIBRETRO_COMM_DIR)/formats/vp9/rvp9.o
 endif
 
+ifeq ($(HAVE_WEBMPLAYER), 1)
+   DEFINES += -DHAVE_WEBMPLAYER
+   OBJ += cores/libretro-webm/webm_core.o
+endif
+
 OBJ += $(LIBRETRO_COMM_DIR)/formats/bmp/rbmp_encode.o \
        $(LIBRETRO_COMM_DIR)/formats/json/rjson.o \
        $(LIBRETRO_COMM_DIR)/formats/image_transfer.o \

config.def.h

@@ -1971,7 +1971,7 @@
 
 #define DEFAULT_AI_SERVICE_URL "http://localhost:4404/"
 
-#if defined(HAVE_FFMPEG) || defined(HAVE_MPV)
+#if defined(HAVE_FFMPEG) || defined(HAVE_MPV) || defined(HAVE_WEBMPLAYER)
 #define DEFAULT_BUILTIN_MEDIAPLAYER_ENABLE true
 #else
 #define DEFAULT_BUILTIN_MEDIAPLAYER_ENABLE false

cores/internal_cores.h

@@ -136,6 +136,62 @@ size_t libretro_ffmpeg_retro_get_memory_size(unsigned id);
 
 #endif
 
+#ifdef HAVE_WEBMPLAYER
+/* Internal WebM (rwebm+rvp8/rvp9) player core. */
+
+void libretro_webm_retro_init(void);
+
+void libretro_webm_retro_deinit(void);
+
+unsigned libretro_webm_retro_api_version(void);
+
+void libretro_webm_retro_get_system_info(struct retro_system_info *info);
+
+void libretro_webm_retro_get_system_av_info(struct retro_system_av_info *info);
+
+void libretro_webm_retro_set_environment(retro_environment_t cb);
+
+void libretro_webm_retro_set_video_refresh(retro_video_refresh_t cb);
+
+void libretro_webm_retro_set_audio_sample(retro_audio_sample_t cb);
+
+void libretro_webm_retro_set_audio_sample_batch(retro_audio_sample_batch_t cb);
+
+void libretro_webm_retro_set_input_poll(retro_input_poll_t cb);
+
+void libretro_webm_retro_set_input_state(retro_input_state_t cb);
+
+void libretro_webm_retro_set_controller_port_device(unsigned port, unsigned device);
+
+void libretro_webm_retro_reset(void);
+
+void libretro_webm_retro_run(void);
+
+size_t libretro_webm_retro_serialize_size(void);
+
+bool libretro_webm_retro_serialize(void *s, size_t len);
+
+bool libretro_webm_retro_unserialize(const void *s, size_t len);
+
+void libretro_webm_retro_cheat_reset(void);
+
+void libretro_webm_retro_cheat_set(unsigned index, bool enabled, const char *code);
+
+bool libretro_webm_retro_load_game(const struct retro_game_info *game);
+
+bool libretro_webm_retro_load_game_special(unsigned game_type,
+      const struct retro_game_info *info, size_t num_info);
+
+void libretro_webm_retro_unload_game(void);
+
+unsigned libretro_webm_retro_get_region(void);
+
+void *libretro_webm_retro_get_memory_data(unsigned id);
+
+size_t libretro_webm_retro_get_memory_size(unsigned id);
+
+#endif
+
 #ifdef HAVE_MPV
 /* Internal mpv core. */
 

cores/libretro-webm/internal_cores.h

@@ -0,0 +1 @@
+#include "../internal_cores.h"