Change the video image to scrolling color bars.

examples/device/video_capture/src/main.c

@@ -31,7 +31,6 @@
 #include "tusb.h"
 #include "usb_descriptors.h"
 
-#include "images.h"
 //--------------------------------------------------------------------+
 // MACRO CONSTANT TYPEDEF PROTYPES
 //--------------------------------------------------------------------+
@@ -104,15 +103,54 @@ void tud_resume_cb(void)
 //--------------------------------------------------------------------+
 // USB Video
 //--------------------------------------------------------------------+
-static unsigned char const *frames[] = {
+static unsigned frame_num = 0;
-  white_128x96_yuv, white_128x96_yuv, white_128x96_yuv,
-  t_128x96_yuv, ti_128x96_yuv, tin_128x96_yuv, logo_128x96_yuv,
-  logo_128x96_yuv, logo_128x96_yuv, logo_128x96_yuv, logo_128x96_yuv
-};
-static unsigned current_frame = 0;
 static unsigned tx_busy = 0;
 static unsigned interval_ms = 1000 / FRAME_RATE;
 
+/* YUY2 frame buffer */
+#ifdef CFG_EXAMPLE_VIDEO_READONLY
+#include "images.h"
+#else
+static uint8_t frame_buffer[FRAME_WIDTH * FRAME_HEIGHT * 16 / 8];
+static void fill_color_bar(uint8_t *buffer, unsigned start_position)
+{
+  /* EBU color bars
+   * See also https://stackoverflow.com/questions/6939422 */
+  static uint8_t const bar_color[8][4] = {
+    /*  Y,   U,   Y,   V */
+    { 235, 128, 235, 128}, /* 100% White */
+    { 219,  16, 219, 138}, /* Yellow */
+    { 188, 154, 188,  16}, /* Cyan */
+    { 173,  42, 173,  26}, /* Green */
+    {  78, 214,  78, 230}, /* Magenta */
+    {  63, 102,  63, 240}, /* Red */
+    {  32, 240,  32, 118}, /* Blue */
+    {  16, 128,  16, 128}, /* Black */
+  };
+  uint8_t *p;
+
+  /* Generate the 1st line */
+  uint8_t *end = &buffer[FRAME_WIDTH * 2];
+  unsigned idx = (FRAME_WIDTH / 2 - 1) - (start_position % (FRAME_WIDTH / 2));
+  p = &buffer[idx * 4];
+  for (unsigned i = 0; i < 8; ++i) {
+    for (int j = 0; j < FRAME_WIDTH / (2 * 8); ++j) {
+      memcpy(p, &bar_color[i], 4);
+      p += 4;
+      if (end <= p) {
+        p = buffer;
+      }
+    }
+  }
+  /* Duplicate the 1st line to the others */
+  p = &buffer[FRAME_WIDTH * 2];
+  for (unsigned i = 1; i < FRAME_HEIGHT; ++i) {
+    memcpy(p, buffer, FRAME_WIDTH * 2);
+    p += FRAME_WIDTH * 2;
+  }
+}
+#endif
+
 void video_task(void)
 {
   static unsigned start_ms = 0;
@@ -120,14 +158,20 @@ void video_task(void)
 
   if (!tud_video_n_streaming(0, 0)) {
     already_sent  = 0;
-    current_frame = 0;
+    frame_num     = 0;
     return;
   }
 
   if (!already_sent) {
     already_sent = 1;
     start_ms = board_millis();
-    tud_video_n_frame_xfer(0, 0, (void*)frames[current_frame], FRAME_WIDTH * FRAME_HEIGHT * 12/8);
+#ifdef CFG_EXAMPLE_VIDEO_READONLY
+    tud_video_n_frame_xfer(0, 0, (void*)&frame_buffer[(frame_num % (FRAME_WIDTH / 2)) * 4],
+                           FRAME_WIDTH * FRAME_HEIGHT * 16/8);
+#else
+    fill_color_bar(frame_buffer, frame_num);
+    tud_video_n_frame_xfer(0, 0, (void*)frame_buffer, FRAME_WIDTH * FRAME_HEIGHT * 16/8);
+#endif
   }
 
   unsigned cur = board_millis();
@@ -135,7 +179,13 @@ void video_task(void)
   if (tx_busy) return;
   start_ms += interval_ms;
 
-  tud_video_n_frame_xfer(0, 0, (void*)frames[current_frame], FRAME_WIDTH * FRAME_HEIGHT * 12/8);
+#ifdef CFG_EXAMPLE_VIDEO_READONLY
+  tud_video_n_frame_xfer(0, 0, (void*)&frame_buffer[(frame_num % (FRAME_WIDTH / 2)) * 4],
+                         FRAME_WIDTH * FRAME_HEIGHT * 16/8);
+#else
+  fill_color_bar(frame_buffer, frame_num);
+  tud_video_n_frame_xfer(0, 0, (void*)frame_buffer, FRAME_WIDTH * FRAME_HEIGHT * 16/8);
+#endif
 }
 
 void tud_video_frame_xfer_complete_cb(uint_fast8_t ctl_idx, uint_fast8_t stm_idx)
@@ -143,9 +193,7 @@ void tud_video_frame_xfer_complete_cb(uint_fast8_t ctl_idx, uint_fast8_t stm_idx
   (void)ctl_idx; (void)stm_idx;
   tx_busy = 0;
   /* flip buffer */
-  ++current_frame;
+  ++frame_num;
-  if (current_frame == sizeof(frames)/sizeof(frames[0]))
-    current_frame = 0;
 }
 
 int tud_video_commit_cb(uint_fast8_t ctl_idx, uint_fast8_t stm_idx,

examples/device/video_capture/src/usb_descriptors.h

@@ -61,7 +61,7 @@ enum {
     + 7/* Endpoint */\
   )
 
-/* Windows support YUV2 and NV12
+/* Windows support YUY2 and NV12
  * https://docs.microsoft.com/en-us/windows-hardware/drivers/stream/usb-video-class-driver-overview */
 
 #define TUD_VIDEO_DESC_CS_VS_FMT_YUY2(_fmtidx, _numfmtdesc, _frmidx, _asrx, _asry, _interlace, _cp) \
@@ -97,12 +97,12 @@ enum {
           /*bStillCaptureMethod*/0, /*bTriggerSupport*/0, /*bTriggerUsage*/0, \
           /*bmaControls(1)*/0), \
         /* Video stream format */ \
-        TUD_VIDEO_DESC_CS_VS_FMT_NV12(/*bFormatIndex*/1, /*bNumFrameDescriptors*/1,\
+        TUD_VIDEO_DESC_CS_VS_FMT_YUY2(/*bFormatIndex*/1, /*bNumFrameDescriptors*/1, \
           /*bDefaultFrameIndex*/1, 0, 0, 0, /*bCopyProtect*/0), \
           /* Video stream frame format */ \
           TUD_VIDEO_DESC_CS_VS_FRM_UNCOMPR_CONT(/*bFrameIndex */1, 0, _width, _height, \
-              _width * _height * 12, _width * _height * 12 * _fps, \
+              _width * _height * 16, _width * _height * 16 * _fps, \
-              _width * _height * 12, \
+              _width * _height * 16, \
               (10000000/_fps), (10000000/_fps), 10000000, 100000), \
           TUD_VIDEO_DESC_CS_VS_COLOR_MATCHING(VIDEO_COLOR_PRIMARIES_BT709, VIDEO_COLOR_XFER_CH_BT709, VIDEO_COLOR_COEF_SMPTE170M), \
     /* VS alt 1 */\

hw/bsp/frdm_kl25z/board.mk

@@ -6,7 +6,8 @@ CFLAGS += \
   -mabi=aapcs \
   -mcpu=cortex-m0plus \
   -DCPU_MKL25Z128VLK4 \
-  -DCFG_TUSB_MCU=OPT_MCU_MKL25ZXX
+  -DCFG_TUSB_MCU=OPT_MCU_MKL25ZXX \
+  -DCFG_EXAMPLE_VIDEO_READONLY
 
 LDFLAGS += \
   -Wl,--defsym,__stack_size__=0x400 \