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difference between these two images captured by DM355

Jogging Song
Intellectual 685 points

Hi,all

     Here I have two images. One images is captured by a camera. One images is from a mpeg4 stream captured by the same
camera using DM355. But the images look a littler different. I am told that the images and videos are captured under the same
conditions such as the same illumination and same exposure time. The different difference is resolution. When one video is
captured, the image is resized from 1024x768 to 640x480. In my view, the different codec won't cause such difference, and
I did some experiments using ffmpeg and confirm my thought.

    As we know, pre process step is utilized to improved the image quality. I wonder whether pre process is used and
is different for videos and images. I am told the images from the sensor go through the same process in the IPIPE.
Do the codecs contain any such steps?Here is the link to the images:
http://picasaweb.google.com/joggingsong/Difference#

Thanks in advance.
Best Regards
Jogging

  • 0
    TI__Intellectual 1870 points

    Hi,

     

     We need your help to understand the problem better.

     The best way is sharing YUV data (before codec applied). We assume the same ISP parameters are used (except resizer), but YUV data can tell the source of problem

     

    Regards,

    Sang-Yong

  • 0 in reply to SANG-YONG
    Intellectual 685 points

    Thanks, Sang-Yong
    I do some search and find that the range for Y is [16,235]  and the range for Cr and Cb are [16,239] for MPEG4 stream.
    In JPEG the entire range of [0, 255] are used for Y, Cr and Cb. Frames are captured in RGB color space, then
    converted to YUV color space. The same YUV data are used to MPEG4 and JPEG. I am told that YUV data
    are in the range of [0, 255]. But according the the spec the ranges should be different. When the bitstream
    are decoded, different conversion matrices are selected. Maybe this will cause some problem.

    I wonder what MPEG4 encoder will do if YUV data in the range of [0, 255] are provided?
    Will MPEG4 endoer  process the data first before the data are encoded or MPEG4 encoder ignores it?

    Now I don't have the YUV data. I will ask some to provide it. If I have the data, I will try to send it to you.

    Best Regards
    Jogging Song

  • 0 in reply to Jogging Song
    TI__Intellectual 1870 points

    MPEG4 encoder doesn't have the limitation, so it supports [0,255].

     

    regards,

    Sang-Yong

  • 0 in reply to SANG-YONG
    Intellectual 685 points

    Hi, Sang-Yong
          You are right. There are two kinds of video ranges defined in the MPEG4 spec.
    But when the range of [0, 255] is used,  this information should be included into
    the bitstream, Visual Object Sequence and Visual Object layer.
    Otherwise video range is assumed to have the value o(a range of Y from
    16 to 255 for 8-bit video).

    From the bitstream generated by DM355, Visual Object Sequence and Visual Object layer.
    is not present, so a range of Y from 16 to 255 for 8-bit video is assumed.

    Is it possible to configure the encoder to generate bitstream with VOS and VO layer?

    Best Regards
    Jogging Song

  • 0 in reply to Jogging Song
    TI__Intellectual 1870 points

    Could you post this as codec question?

    It is better be supported if you make this as new question.

     

    regards,

    Sang-Yong

  • 0 in reply to SANG-YONG
    Expert 1335 points

    Hi sang-Yong,

    I am working on dm355 linux platform.

    following getting started guide tms320dm355 dvevm v1.30, i got the kernel and root file system, got success Booting via TFTP using NFS file system.

    but unable to run the demo, getting osd display output but no video display and error  as shown below.

    root@10.10.10.242:/opt/dvsdk/dm355# ls
    cmemk.ko decode.txt encode encodedecode.txt log.txt web
    data dm350mmap.ko encode.txt interface mapdmaq
    decode dvevmdemo encodedecode loadmodules.sh thirdpartydemos

    root@10.10.10.242:/opt/dvsdk/dm355# ./decode -v data/videos/davincieffect_pal.mpeg4

    Decode demo started.
    CMEM Error: init: Failed to open /dev/cmem: 'No such file or directory'
    Decode Error: Failed FBIOPUT_VSCREENINFO on /dev/fb/3 (Invalid argument)
    Decode Error: Failed to open video decode algorithm
    root@10.10.10.242:/opt/dvsdk/dm355#

     kindly do the needfull.

    Thanks and regards,

    Mohammed asif.