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From ac2682411d03cf2951abf2856aeaf10206e700fc Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Thu, 13 May 2021 11:56:21 +0100
Subject: [PATCH] staging/bcm2835-codec: Change the default codec res
to 32x32
In order to effectively guarantee that a V4L2_EVENT_SOURCE_CHANGE
event occurs, adopt a default resolution of 32x32 so that it
is incredibly unlikely to be decoding a stream of that resolution
and therefore failing to note a "change" requiring the event.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
.../bcm2835-codec/bcm2835-v4l2-codec.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/drivers/staging/vc04_services/bcm2835-codec/bcm2835-v4l2-codec.c
+++ b/drivers/staging/vc04_services/bcm2835-codec/bcm2835-v4l2-codec.c
@@ -97,8 +97,19 @@ static const char * const components[] =
#define MAX_W 1920
#define MAX_H 1920
#define BPL_ALIGN 32
-#define DEFAULT_WIDTH 640
-#define DEFAULT_HEIGHT 480
+/*
+ * The decoder spec supports the V4L2_EVENT_SOURCE_CHANGE event, but the docs
+ * seem to want it to always be generated on startup, which prevents the client
+ * from configuring the CAPTURE queue based on any parsing it has already done
+ * which may save time and allow allocation of CAPTURE buffers early. Surely
+ * SOURCE_CHANGE means something has changed, not just "always notify".
+ *
+ * For those clients that don't set the CAPTURE resolution, adopt a default
+ * resolution that is seriously unlikely to be correct, therefore almost
+ * guaranteed to get the SOURCE_CHANGE event.
+ */
+#define DEFAULT_WIDTH 32
+#define DEFAULT_HEIGHT 32
/*
* The unanswered question - what is the maximum size of a compressed frame?
* V4L2 mandates that the encoded frame must fit in a single buffer. Sizing
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