[Libva] [Bug 58176] [gst-vaapi] gi4_video.bits decoding failed (MPEG2)

[Gwenole Beauchesne]

Hi,

2013/1/31 Yuan, Feng <feng.yuan at intel.com>:

>       Question is how to fill <xxx_intra_quantiser_matrix>, is it zigzag
> ordered or scan ordered? Mpeg2 data store the quantization table in zigzag
> order.

If the API is undefined, we have to cope with the driver that has the
least chances to get updated, and that does depend on explicit
quantization matrices. Define this as the expected order. Repeat and
constrain this with all supported codecs to make a consistent
behavior. So, if we chose scan order for MPEG-2, this also has to be
the case for MPEG-4, etc.

Then, the second element to consider is to carry on the less
operations possible. So, based on your comments, the intel-driver does
perform a conversion too. However, there are two similar conversions
happening in FFmpeg too. So, in the end, there are 3 conversion steps!
Two of them are most likely useless.

>      Ffmpeg would fill the quantiser_matrix by zigzag order, do we need to
> change gstreamer-codec-parse to read data into zigzag order? Does any other
> package/lib already using gstreamer-codec-parser(mpeg2)?  Which package
> should be the right role to do the conversion from zigzag to scanning order?

For performance reasons, only one conversion should happen. So, FFmpeg
and intel-driver would need to change.

For compatibility reasons, we have to continue with any bad choices we
made before. So, GStreamer (codecparser or gstreamer-vaapi) would need
to change. Xiaowei also pointed out another issue with default
matrices. I didn't have the time to look into it.

Please check the expected behavior against the EMGD driver for
example. Based on the OSS PVR driver, it seems that we also perform a
conversion in there. So, we may end up to still use the "triple
conversions" (parser / codec / driver) scenario...

Regards,
Gwenole.

> From: Li, Jocelyn
> Sent: Thursday, January 31, 2013 10:24 AM
> To: Beauchesne, Gwenole; Xiang, Haihao
> Cc: Zhao, Halley; Yuan, Feng; Zhong, CongX
> Subject: FW: [Bug 58176] [gst-vaapi] gi4_video.bits decoding failed (MPEG2)
>
>
>
> Hi Gwenole and Haihao,
>
>
>
> We need your comments on the solution to fix this issue.
>
>
>
> Thanks,
>
> Jocelyn
>
>
>
> From: bugzilla-daemon at freedesktop.org
> [mailto:bugzilla-daemon at freedesktop.org]
> Sent: Wednesday, January 30, 2013 5:19 PM
> To: Li, Jocelyn
> Subject: [Bug 58176] [gst-vaapi] gi4_video.bits decoding failed (MPEG2)
>
>
>
> Comment # 5 on bug 58176 from Zhong Cong
>
> Created attachment 73914 [details] [review]
>
> This patch remove inverse zigzag in gstvaapi codecparser
>
>
>
> gstvaapi codecparse handles the data with inverse zigzag, and the
> intel-driver
>
> alse asks for original data to inverse zigzag. Here comes the
>
> contradiction.This patch remove inverse zigzag in gstvaapi codecparser,and
> it
>
> can solve this issue.
>
> ________________________________
>
> You are receiving this mail because:
>
> You are watching the assignee of the bug.
>
>
> _______________________________________________
> Libva mailing list
> Libva at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/libva
>