cam: sdl_sink: Add MJPG support to SDL sink

So we have at least two supported capturing pixel formats (although
many possible output pixel formats thanks to SDL conversion). MJPG
support only built in if SDL2_image is available, provides
decompression.

Signed-off-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/cam/meson.build

@@ -25,6 +25,7 @@ cam_cpp_args = []
 
 libdrm = dependency('libdrm', required : false)
 libsdl2 = dependency('SDL2', required : false)
+libsdl2_image = dependency('SDL2_image', required : false)
 
 if libdrm.found()
     cam_cpp_args += [ '-DHAVE_KMS' ]
@@ -41,6 +42,13 @@ if libsdl2.found()
         'sdl_texture.cpp',
         'sdl_texture_yuyv.cpp'
     ])
+
+    if libsdl2_image.found()
+        cam_cpp_args += ['-DHAVE_SDL_IMAGE']
+        cam_sources += files([
+            'sdl_texture_mjpg.cpp'
+        ])
+    endif
 endif
 
 cam  = executable('cam', cam_sources,
@@ -50,6 +58,7 @@ cam  = executable('cam', cam_sources,
                       libdrm,
                       libevent,
                       libsdl2,
+                      libsdl2_image,
                       libyaml,
                   ],
                   cpp_args : cam_cpp_args,

src/cam/sdl_sink.cpp

@@ -21,6 +21,9 @@
 
 #include "event_loop.h"
 #include "image.h"
+#ifdef HAVE_SDL_IMAGE
+#include "sdl_texture_mjpg.h"
+#endif
 #include "sdl_texture_yuyv.h"
 
 using namespace libcamera;
@@ -59,6 +62,11 @@ int SDLSink::configure(const libcamera::CameraConfiguration &config)
 	rect_.h = cfg.size.height;
 
 	switch (cfg.pixelFormat) {
+#ifdef HAVE_SDL_IMAGE
+	case libcamera::formats::MJPEG:
+		texture_ = std::make_unique<SDLTextureMJPG>(rect_);
+		break;
+#endif
 	case libcamera::formats::YUYV:
 		texture_ = std::make_unique<SDLTextureYUYV>(rect_);
 		break;

src/cam/sdl_texture_mjpg.cpp

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2022, Ideas on Board Oy
+ *
+ * sdl_texture_mjpg.cpp - SDL Texture MJPG
+ */
+
+#include "sdl_texture_mjpg.h"
+
+#include <SDL2/SDL_image.h>
+
+using namespace libcamera;
+
+SDLTextureMJPG::SDLTextureMJPG(const SDL_Rect &rect)
+	: SDLTexture(rect, SDL_PIXELFORMAT_RGB24, 0)
+{
+}
+
+void SDLTextureMJPG::update(const Span<uint8_t> &data)
+{
+	SDL_RWops *bufferStream = SDL_RWFromMem(data.data(), data.size());
+	SDL_Surface *frame = IMG_Load_RW(bufferStream, 0);
+	SDL_UpdateTexture(ptr_, nullptr, frame->pixels, frame->pitch);
+	SDL_FreeSurface(frame);
+}

src/cam/sdl_texture_mjpg.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2022, Ideas on Board Oy
+ *
+ * sdl_texture_mjpg.h - SDL Texture MJPG
+ */
+
+#pragma once
+
+#include "sdl_texture.h"
+
+class SDLTextureMJPG : public SDLTexture
+{
+public:
+	SDLTextureMJPG(const SDL_Rect &rect);
+	void update(const libcamera::Span<uint8_t> &data) override;
+};