em28xx: fix: don't do image interlacing on webcams

From: Mauro Carvalho Chehab <mchehab@redhat.com>

Due to historical reasons, em28xx driver gets two consecutive frames and
fold them into an unique framing, doing interlacing. While this works
fine for TV images, this produces two bad effects with webcams:

1) webcam images are progressive. Merging two consecutive images produce
interlacing artifacts on the image;

2) since the driver needs to get two frames, it reduces the maximum
frame rate by two.

Priority: normal

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

4 files changed, 42 insertions, 10 deletions

diff --git a/linux/drivers/media/video/em28xx/em28xx-cards.c b/linux/drivers/media/video/em28xx/em28xx-cards.c
index 27725c0ed..594461739 100644
--- a/linux/drivers/media/video/em28xx/em28xx-cards.c
+++ b/linux/drivers/media/video/em28xx/em28xx-cards.c
@@ -2623,6 +2623,10 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
 		if (em28xx_hint_sensor(dev) < 0)
 			dev->board.is_webcam = 0;
 
+	/* It makes no sense to use de-interlacing mode on webcams */
+	if (dev->board.is_webcam)
+		dev->progressive = 1;
+
 	/* Do board specific init and eeprom reading */
 	em28xx_card_setup(dev);
 
diff --git a/linux/drivers/media/video/em28xx/em28xx-core.c b/linux/drivers/media/video/em28xx/em28xx-core.c
index a1de593ec..10da3ad82 100644
--- a/linux/drivers/media/video/em28xx/em28xx-core.c
+++ b/linux/drivers/media/video/em28xx/em28xx-core.c
@@ -720,7 +720,10 @@ int em28xx_resolution_set(struct em28xx *dev)
 {
 	int width, height;
 	width = norm_maxw(dev);
-	height = norm_maxh(dev) >> 1;
+	height = norm_maxh(dev);
+
+	if (!dev->progressive)
+		height >>= norm_maxh(dev);
 
 	em28xx_set_outfmt(dev);
 
diff --git a/linux/drivers/media/video/em28xx/em28xx-video.c b/linux/drivers/media/video/em28xx/em28xx-video.c
index f2d9564e9..77ec51dad 100644
--- a/linux/drivers/media/video/em28xx/em28xx-video.c
+++ b/linux/drivers/media/video/em28xx/em28xx-video.c
@@ -212,15 +212,24 @@ static void em28xx_copy_video(struct em28xx *dev,
 	startread = p;
 	remain = len;
 
-	/* Interlaces frame */
-	if (buf->top_field)
+	if (dev->progressive)
 		fieldstart = outp;
-	else
-		fieldstart = outp + bytesperline;
+	else {
+		/* Interlaces two half frames */
+		if (buf->top_field)
+			fieldstart = outp;
+		else
+			fieldstart = outp + bytesperline;
+	}
 
 	linesdone = dma_q->pos / bytesperline;
 	currlinedone = dma_q->pos % bytesperline;
-	offset = linesdone * bytesperline * 2 + currlinedone;
+
+	if (dev->progressive)
+		offset = linesdone * bytesperline + currlinedone;
+	else
+		offset = linesdone * bytesperline * 2 + currlinedone;
+
 	startwrite = fieldstart + offset;
 	lencopy = bytesperline - currlinedone;
 	lencopy = lencopy > remain ? remain : lencopy;
@@ -398,7 +407,7 @@ static inline int em28xx_isoc_copy(struct em28xx *dev, struct urb *urb)
 			em28xx_isocdbg("Video frame %d, length=%i, %s\n", p[2],
 				       len, (p[2] & 1) ? "odd" : "even");
 
-			if (!(p[2] & 1)) {
+			if (dev->progressive || !(p[2] & 1)) {
 				if (buf != NULL)
 					buffer_filled(dev, dma_q, buf);
 				get_next_buf(dma_q, &buf);
@@ -742,7 +751,10 @@ static int vidioc_g_fmt_vid_cap(struct file *file, void *priv,
 	f->fmt.pix.colorspace = V4L2_COLORSPACE_SMPTE170M;
 
 	/* FIXME: TOP? NONE? BOTTOM? ALTENATE? */
-	f->fmt.pix.field = dev->interlaced ?
+	if (dev->progressive)
+		f->fmt.pix.field = V4L2_FIELD_NONE;
+	else
+		f->fmt.pix.field = dev->interlaced ?
 			   V4L2_FIELD_INTERLACED : V4L2_FIELD_TOP;
 
 	mutex_unlock(&dev->lock);
@@ -806,7 +818,11 @@ static int vidioc_try_fmt_vid_cap(struct file *file, void *priv,
 	f->fmt.pix.bytesperline = (dev->width * fmt->depth + 7) >> 3;
 	f->fmt.pix.sizeimage = f->fmt.pix.bytesperline * height;
 	f->fmt.pix.colorspace = V4L2_COLORSPACE_SMPTE170M;
-	f->fmt.pix.field = V4L2_FIELD_INTERLACED;
+	if (dev->progressive)
+		f->fmt.pix.field = V4L2_FIELD_NONE;
+	else
+		f->fmt.pix.field = dev->interlaced ?
+			   V4L2_FIELD_INTERLACED : V4L2_FIELD_TOP;
 
 	return 0;
 }
@@ -1765,6 +1781,7 @@ static int em28xx_v4l2_open(struct file *filp)
 	struct em28xx *dev;
 	enum v4l2_buf_type fh_type;
 	struct em28xx_fh *fh;
+	enum v4l2_field field;
 
 	dev = em28xx_get_device(minor, &fh_type, &radio);
 
@@ -1821,8 +1838,13 @@ static int em28xx_v4l2_open(struct file *filp)
 
 	dev->users++;
 
+	if (dev->progressive)
+		field = V4L2_FIELD_NONE;
+	else
+		field = V4L2_FIELD_INTERLACED;
+
 	videobuf_queue_vmalloc_init(&fh->vb_vidq, &em28xx_video_qops,
-			NULL, &dev->slock, fh->type, V4L2_FIELD_INTERLACED,
+			NULL, &dev->slock, fh->type, field,
 			sizeof(struct em28xx_buffer), fh);
 
 	mutex_unlock(&dev->lock);
diff --git a/linux/drivers/media/video/em28xx/em28xx.h b/linux/drivers/media/video/em28xx/em28xx.h
index 3c4cd00b2..c76da6985 100644
--- a/linux/drivers/media/video/em28xx/em28xx.h
+++ b/linux/drivers/media/video/em28xx/em28xx.h
@@ -494,6 +494,9 @@ struct em28xx {
 	int sensor_xres, sensor_yres;
 	int sensor_xtal;
 
+	/* Allows progressive (e. g. non-interlaced) mode */
+	int progressive;
+
 	/* Vinmode/Vinctl used at the driver */
 	int vinmode, vinctl;