Artifact w/ HW decode i.MX6

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1

there seem to be some artifacts on the screen during the decode. Sample is here, the issue is a grey bar at the bottom on the video, this is not present during a SW decode or on VDPAU.

General
Unique ID                                : 244043958016963078675602115081842977901 (0xB799281A28E0E372B164F0B2E393EC6D)
Complete name                            : grey_bar.mkv
Format                                   : Matroska
Format version                           : Version 2
File size                                : 20.0 MiB
Duration                                 : 2h 10mn
Overall bit rate                         : 21.5 Kbps
Movie name                               : Fast
Encoded date                             : UTC 2013-07-03 22:00:05
Writing application                      : mkvmerge v5.3.0 ('I could have danced') built on Feb  9 2012 10:38:07
Writing library                          : libebml v1.2.3 + libmatroska v1.3.0

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Main@L3.1
Format settings, CABAC                   : No
Format settings, ReFrames                : 2 frames
Muxing mode                              : Header stripping
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 2h 10mn
Width                                    : 1 280 pixels
Height                                   : 542 pixels
Display aspect ratio                     : 2.35:1
Frame rate mode                          : Constant
Frame rate                               : 23.976 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Title                                    : Fast
Language                                 : English
Default                                  : Yes
Forced                                   : No
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : A_AAC
Duration                                 : 2h 10mn
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Title                                    : AAC 2.0 @ 160 kbps
Language                                 : English
Default                                  : No
Forced                                   : No
2

@fritsch thought you would be interested in this one too.

3

My guess would be because the height is not /16.

There were also some kernel changes that may help with this. A new kernel has been built and you could give this a go (it is in staging). If you break anything you can go to Download - OSMC to re-install the base image. I don’t normally recommend this but you seem to not mind a bit of tinkering

S

4

Yeah:
Width : 1 280 pixels
Height : 542 pixels

Shitty encoding. Currently not interested (cause of time) - the way the decoder works aligns to 16 and that results in those grey pixels.

Decoding: 16
Cropping: 8

5

@vajonam: https://github.com/xbmc/xbmc/blob/master/xbmc/cores/dvdplayer/DVDCodecs/Video/DVDVideoCodecIMX.cpp#L1787 ← align them all to 4 (e.g. change the 8 to 4) and see if it burns :slight_smile:

6

Give the new kernel a go first. Someone claims http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/commit/drivers/mxc/ipu3?h=imx_3.0.35_4.1.0&id=a316c7d58f622bd3c16e01e6de638e3ffc74c777 helps and this commit is in the Vero kernel tree now

S

7

Kernel won’t change it - cause we “align” in userspace, directly in the decoder, see the line I linked in my previous post. I cannot remember anymore, if that was a must / limitation somewhere, but I cannot imagine that concerning the dropping.

Btw. the original sample is not even % 8 … so very unfriendly for hw decoders.

8

So then the grey bar is some sort of padding? can that color not be changed to black? which would then not make it as obvious?

9

Fix your file :slight_smile: Or play with the codeline I sent you. That Code is OpenSource and you are very welcome to fiddle it out.

10

So changing the alignment to 4 didn’t help, as you said it didn’t didn’t align nicely, so changing it to 2 fixed it, not sure what other issues this will cause. @sam_nazarko said he would fiddle around w/ it too.

11

Yeah - we met on IRC. Looks fixed already - PR incoming to upstream.