From 1c9dc0fd89cfb32d31e25c4d14501c891d329307 Mon Sep 17 00:00:00 2001
From: Kieran Bingham <kieran.bingham@ideasonboard.com>
Date: Mon, 2 May 2022 16:42:49 +0200
Subject: libcamera: v4l2_videodevice: Identify non-zero stream starts
V4L2 Video devices should always start streaming from index zero.
Identify and report a warning if they don't, and correct for any offset.
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
src/libcamera/v4l2_videodevice.cpp | 15 +++++++++++++++
1 file changed, 15 insertions(+)
(limited to 'src')
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 430715af..63911339 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -1771,6 +1771,19 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
if (V4L2_TYPE_IS_OUTPUT(buf.type))
return buffer;
+ /*
+ * Detect kernel drivers which do not reset the sequence number to zero
+ * on stream start.
+ */
+ if (!firstFrame_) {
+ if (buf.sequence)
+ LOG(V4L2, Warning)
+ << "Zero sequence expected for first frame (got "
+ << buf.sequence << ")";
+ firstFrame_ = buf.sequence;
+ }
+ buffer->metadata_.sequence -= firstFrame_.value();
+
unsigned int numV4l2Planes = multiPlanar ? buf.length : 1;
FrameMetadata &metadata = buffer->metadata_;
@@ -1847,6 +1860,8 @@ int V4L2VideoDevice::streamOn()
{
int ret;
+ firstFrame_.reset();
+
ret = ioctl(VIDIOC_STREAMON, &bufferType_);
if (ret < 0) {
LOG(V4L2, Error)
--
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