docs: README update

Makefile.am

@@ -5,6 +5,6 @@ forge_CFLAGS = -Ofast -march=native -flto -funroll-loops -fprefetch-loop-arrays
 forge_LDADD = -lm -lGL -lglfw -lasound -lbsd
 include_HEADERS = src/args.h src/arr.h src/config.h src/config_file.h src/constants.h src/file.h src/forge.h src/main.h src/midi.h src/project.h src/rand.h src/shaders.h src/shared.h src/state.h src/string.h src/tempo.h src/timer.h src/types.h src/video.h src/window.h $(top_srcdir)/include/glad/gl.h $(top_srcdir)/include/glad/egl.h $(top_srcdir)/include/linmath.h $(top_srcdir)/include/hashmap.h $(top_srcdir)/include/log.h
 
-EXTRA_DIST = default/forge_project.cfg default/frag1.glsl default/frag10.glsl default/frag2.glsl default/frag3.glsl default/frag4.glsl default/frag5.glsl default/frag6.glsl default/frag7.glsl default/frag8.glsl default/frag9.glsl default/inc_cp437.glsl default/inc_debug.glsl default/inc_functions.glsl default/inc_fx.glsl default/inc_magic.glsl default/inc_rand.glsl default/inc_res.glsl default/inc_sentences.glsl default/inc_src.glsl default/inc_template.glsl default/inc_time.glsl default/inc_yuv.glsl
+EXTRA_DIST = default/forge_project.cfg default/frag1.glsl default/frag10.glsl default/frag2.glsl default/frag3.glsl default/frag4.glsl default/frag5.glsl default/frag6.glsl default/frag7.glsl default/frag8.glsl default/frag9.glsl default/inc_cp437.glsl default/inc_debug.glsl default/inc_functions.glsl default/inc_fx.glsl default/inc_magic.glsl default/inc_rand.glsl default/inc_res.glsl default/inc_sentences.glsl default/inc_src.glsl default/inc_template.glsl default/inc_time.glsl default/inc_yuyv.glsl
 confdir = $(prefix)/share/$(PACKAGE)
-conf_DATA = default/forge_project.cfg default/frag1.glsl default/frag10.glsl default/frag2.glsl default/frag3.glsl default/frag4.glsl default/frag5.glsl default/frag6.glsl default/frag7.glsl default/frag8.glsl default/frag9.glsl default/inc_cp437.glsl default/inc_debug.glsl default/inc_functions.glsl default/inc_fx.glsl default/inc_magic.glsl default/inc_rand.glsl default/inc_res.glsl default/inc_sentences.glsl default/inc_src.glsl default/inc_template.glsl default/inc_time.glsl default/inc_yuv.glsl
+conf_DATA = default/forge_project.cfg default/frag1.glsl default/frag10.glsl default/frag2.glsl default/frag3.glsl default/frag4.glsl default/frag5.glsl default/frag6.glsl default/frag7.glsl default/frag8.glsl default/frag9.glsl default/inc_cp437.glsl default/inc_debug.glsl default/inc_functions.glsl default/inc_fx.glsl default/inc_magic.glsl default/inc_rand.glsl default/inc_res.glsl default/inc_sentences.glsl default/inc_src.glsl default/inc_template.glsl default/inc_time.glsl default/inc_yuyv.glsl

README.md

@@ -82,6 +82,7 @@ Here are some pointers if you want to customize your FORGE experience:
   - [My nanoKontrol2 is acting strange](#my-nanokontrol2-is-acting-strange)
   - [How do I report a bug?](#how-do-i-report-a-bug)
   - [Help I got low FPS on my video device](#help-i-got-low-fps-on-my-video-device)
+  - [My video feed got strange lines](#my-video-feed-got-strange-lines)
   - [How do I change the default project built-in sentences?](#how-do-i-change-the-default-project-built-in-sentences)
 
 ## What is FORGE ?
@@ -474,7 +475,17 @@ Don't forget to add all information available to your bug (version, operating sy
 
 ### Help I got low FPS on my video device
 
-There's already an [open issue](https://github.com/klemek/forge-steel/issues/1) on this subject.
+Unfortunately, V4L2 is very slow compared to driver-specific decoding.
+
+You can check your device real FPS on [V4L2 UCP](https://github.com/HedgeHawk/v4l2ucp) or [GTK UVC Viewer](https://github.com/jaswdr/guvcview).
+
+Sadly, OpenEGL doesn't support double-buffered DMA buffers so FPS in FORGE may be halved.
+
+### My video feed got strange lines
+
+You need to decode the [V4L2 YUYV format](https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-yuyv.html).
+
+The code is available in the default project [default/inc_yuyv.glsl](./default/inc_yuyv.glsl)
 
 ### How do I change the default project built-in sentences?
 

default/frag1.glsl

@@ -8,7 +8,7 @@
 in vec2 vUV;
 out vec4 fragColor;
 
-#include inc_yuv.glsl
+#include inc_yuyv.glsl
 
 uniform sampler2D iTex0;
 uniform sampler2D iTex1;
@@ -18,6 +18,8 @@ uniform vec2 iInputResolution1;
 void main() {
     if (iInputFormat1 == YUYV_FOURCC) {
         fragColor = yuyvTex(iTex1, vUV, int(iInputResolution1.x));
+    } else if (iInputResolution1.x > 0) {
+        fragColor = texture(iTex1, vUV);
     } else {
         fragColor = texture(iTex0, vUV);
     }

default/frag2.glsl

@@ -8,7 +8,7 @@
 in vec2 vUV;
 out vec4 fragColor;
 
-#include inc_yuv.glsl
+#include inc_yuyv.glsl
 
 uniform sampler2D iTex0;
 uniform sampler2D iTex2;
@@ -18,6 +18,8 @@ uniform vec2 iInputResolution2;
 void main() {
     if (iInputFormat2 == YUYV_FOURCC) {
         fragColor = yuyvTex(iTex2, vUV, int(iInputResolution2.x));
+    } else if (iInputResolution2.x > 0) {
+        fragColor = texture(iTex2, vUV);
     } else {
         fragColor = texture(iTex0, vUV);
     }

default/inc_debug.glsl

@@ -1,6 +1,6 @@
 #include inc_magic.glsl
 #include inc_functions.glsl
-#include inc_yuv.glsl
+#include inc_yuyv.glsl
 #include inc_cp437.glsl
 
 #ifndef INC_DEBUG

default/inc_yuyv.glsl

@@ -1,9 +1,9 @@
-#ifndef INC_YUV
-#define INC_YUV
+#ifndef INC_YUYV
+#define INC_YUYV
 
 const int YUYV_FOURCC = 1448695129;
 
-const mat3x3 yuv_to_rgb = {{1,1,1},{0,-0.39465,2.03211},{1.13983,-0.5806,0}};
+const mat3x3 yuyv_to_rgb = {{1,1,1},{0,-0.39465,2.03211},{1.13983,-0.5806,0}};
 
 vec4 yuyvTex(sampler2D tex, vec2 vUV, int base_width) {
     float w = base_width - 1;
@@ -22,7 +22,7 @@ vec4 yuyvTex(sampler2D tex, vec2 vUV, int base_width) {
         tV.y - 0.5
     );
 
-    return vec4(yuv_to_rgb * yuv, 1.0);
+    return vec4(yuyv_to_rgb * yuv, 1.0);
 }
 
 #endif