Re: [PATCH] media: hantro: Hook up RK3399 JPEG encoder output

[Chen-Yu Tsai]

On Sat, Nov 20, 2021 at 12:00 AM Nicolas Dufresne <nicolas@xxxxxxxxxxxx> wrote:
>
> Le vendredi 19 novembre 2021 à 15:46 +0800, Chen-Yu Tsai a écrit :
> > The JPEG encoder found in the Hantro H1 encoder block only produces a
> > raw entropy-encoded scan. The driver is responsible for building a JPEG
> > compliant bitstream and placing the entropy-encoded scan in it. Right
> > now the driver uses a bounce buffer for the hardware to output the raw
> > scan to.
> >
> > In commit e765dba11ec2 ("hantro: Move hantro_enc_buf_finish to JPEG
> > codec_ops.done"), the code that copies the raw scan from the bounce
> > buffer to the capture buffer was moved, but was only hooked up for the
> > Hantro H1 (then RK3288) variant. The RK3399 variant was broken,
> > producing a JPEG bitstream without the scan, and the capture buffer's
> > .bytesused field unset.
> >
> > Fix this by duplicating the code that is executed when the JPEG encoder
> > finishes encoding a frame. As the encoded length is read back from
> > hardware, and the variants having different register layouts, the
> > code is duplicated rather than shared.
> >
> > Fixes: e765dba11ec2 ("hantro: Move hantro_enc_buf_finish to JPEG codec_ops.done")
> > Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> > ---
> > This was developed on the downstream ChromeOS 5.10 kernel (with a hack
> > for .data_offset) and tested with ChromeOS's jpeg_encode_accelerator_unittest
> > patched to accept non-JFIF JPEG streams (https://crrev.com/c/3291480).
> >
> > This was then forward-ported to mainline (name and filename changes) and
> > compile tested only.
>
> Tested with GStreamer on top of 5.16-rc1 from media_stage.git. Not perfect but
> at least the the output it valid. Test command was:
>
>   gst-launch-1.0 videotestsrc num-buffers=2 ! v4l2jpegenc ! filesink
> location=test.jpg
>
> Notice that I encode two frames, it seems like the draining flow is broken in
> this driver. GStreamer will queue the frame and issue CMD_START immediately, the
> driver will skip the encode, leaving me with an empty file.

The hantro driver doesn't implement ENC_CMD, which IIRC is used for the
draining flow. I guess that's something to fix, since the mem2mem stateful
encoder spec seems to require it. Or does that spec not apply to the JPEG
encoders?

> Tested-by: Nicolas Dufresne <nicolas.dufresne@xxxxxxxxxxxxx>

Thanks!

ChenYu