Hi Jammy,

On Fri, Nov 19, 2021 at 10:02:40AM +0800, Jammy Huang wrote:

Hi Sakari,

On 2021/11/18 下午 08:33, Sakari Ailus wrote:

quoted

Hi Jammy,

On Thu, Nov 18, 2021 at 03:40:26PM +0800, Jammy Huang wrote:

quoted

This introduces support for the Aspeed JPEG format, where the new frame
can refer to previous frame to reduce the amount of compressed data. The
concept is similar to I/P frame of video compression. I will compare the
new frame with previous one to decide which macroblock's data is
changed, and only the changed macroblocks will be compressed.

This Aspeed JPEG format is used by the video engine on Aspeed platforms,
which is generally adapted for remote KVM.

Signed-off-by: Jammy Huang <redacted>
---
v5:
   - no update
v4:
   - new
---
  Documentation/media/uapi/v4l/pixfmt-reserved.rst | 12 ++++++++++++
  drivers/media/v4l2-core/v4l2-ioctl.c             |  1 +
  include/uapi/linux/videodev2.h                   |  1 +
  3 files changed, 14 insertions(+)

diff --git a/Documentation/media/uapi/v4l/pixfmt-reserved.rst b/Documentation/media/uapi/v4l/pixfmt-reserved.rst
index b2cd155e691b..23c05063133d 100644
--- a/Documentation/media/uapi/v4l/pixfmt-reserved.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-reserved.rst

@@ -264,6 +264,18 @@ please make a proposal on the linux-media mailing list.
  	of tiles, resulting in 32-aligned resolutions for the luminance plane
  	and 16-aligned resolutions for the chrominance plane (with 2x2
  	subsampling).
+    * .. _V4L2-PIX-FMT-AJPG:
+
+      - ``V4L2_PIX_FMT_AJPG``
+      - 'AJPG'
+      - ASPEED JPEG format used by the aspeed-video driver on Aspeed platforms,
+        which is generally adapted for remote KVM.
+        On each frame compression, I will compare the new frame with previous
+        one to decide which macroblock's data is changed, and only the changed
+        macroblocks will be compressed.
+
+        You could reference to chapter 36, Video Engine, of AST2600's datasheet
+        for more information.

Is this datasheet publicly available? Do you have a URL?

Sorry, this datasheet is not publicly available.
Hans mentioned this as well in the discussion below:

https://lkml.org/lkml/2021/11/10/101

If the vendor documentation is not publicly available, you'll need to have
the format documented here. Alternatively an open source implementation
(e.g. LGPL) is presumably fine, too.

-- 
Regards,

Sakari Ailus

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