Lossless end-to-end 16-bit grayscale compression?

[Ryan Talbot]

> avenc_mjpeg does support GRAY16_BE/LE, but I don't know how to make it lossless.

My mistake, avdec_mjpeg supports GRAY16_BE/LE, the encoder only supports I420,Y42B, and Y444.  The conversion from GRAY16_LE->I420 seems to be lossless, so that's good.  The trouble I'm running into now, though, is that avenc_ljpeg doesn't seem to want to accept YUV-colorspace buffers, even though its sink pad template says it can:

Pad Templates:
  SINK template: 'sink'
    Availability: Always
    Capabilities:
      video/x-raw
                 format: { BGR, BGRA, I420, Y444, Y42B }

This pipeline works fine:
gst-launch-1.0 -vvv filesrc location=source.g16 ! videoparse width=640 height=480 format=27 framerate=30/1 ! video/x-raw,format=GRAY16_LE,width=640,height=480,framerate=30/1 ! videoconvert ! video/x-raw,format=BGR ! avenc_ljpeg ! filesink location=losslessgr16.mjpg

This does not:
gst-launch-1.0 -vvv filesrc location=source.g16 ! videoparse width=640 height=480 format=27 framerate=30/1 ! video/x-raw,format=GRAY16_LE,width=640,height=480,framerate=30/1 ! videoconvert ! video/x-raw,format=I420 ! avenc_ljpeg ! filesink location=losslessgr16.mjpg
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
/GstPipeline:pipeline0/GstVideoParse:videoparse0.GstPad:src: caps = "video/x-raw\,\ format\=\(string\)GRAY16_LE\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ colorimetry\=\(string\)1:4:0:0\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:src: caps = "video/x-raw\,\ format\=\(string\)GRAY16_LE\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ colorimetry\=\(string\)1:4:0:0\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstVideoConvert:videoconvert0.GstPad:src: caps = "video/x-raw\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ format\=\(string\)I420"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter1.GstPad:src: caps = "video/x-raw\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ format\=\(string\)I420"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter1.GstPad:sink: caps = "video/x-raw\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ framerate\=\(fraction\)30/1\,\ format\=\(string\)I420"
/GstPipeline:pipeline0/GstVideoConvert:videoconvert0.GstPad:sink: caps = "video/x-raw\,\ format\=\(string\)GRAY16_LE\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ colorimetry\=\(string\)1:4:0:0\,\ framerate\=\(fraction\)30/1"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:sink: caps = "video/x-raw\,\ format\=\(string\)GRAY16_LE\,\ width\=\(int\)640\,\ height\=\(int\)480\,\ interlace-mode\=\(string\)progressive\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\ colorimetry\=\(string\)1:4:0:0\,\ framerate\=\(fraction\)30/1"
ERROR: from element /GstPipeline:pipeline0/GstVideoParse:videoparse0: Internal data stream error.
Additional debug info:
gstrawparse.c(487): gst_raw_parse_loop (): /GstPipeline:pipeline0/GstVideoParse:videoparse0:
stream stopped, reason not-negotiated
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
/GstPipeline:pipeline0/GstCapsFilter:capsfilter1.GstPad:src: caps = "NULL"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter1.GstPad:sink: caps = "NULL"
/GstPipeline:pipeline0/GstVideoConvert:videoconvert0.GstPad:src: caps = "NULL"
/GstPipeline:pipeline0/GstVideoConvert:videoconvert0.GstPad:sink: caps = "NULL"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:src: caps = "NULL"
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:sink: caps = "NULL"
/GstPipeline:pipeline0/GstVideoParse:videoparse0.GstPad:src: caps = "NULL"
Freeing pipeline ...

Is this a bug in avenc_ljpeg, or did I not constrain the caps correctly?
________________________________
From: gstreamer-devel [gstreamer-devel-bounces at lists.freedesktop.org] on behalf of Ryan Talbot [rtalbot at vtti.vt.edu]
Sent: Friday, February 3, 2017 11:12 AM
To: gstreamer-devel at lists.freedesktop.org
Subject: Lossless end-to-end 16-bit grayscale compression?

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Hi list,

I'm trying to losslessy compress the output of the disparity plugin.  Its source caps say it outputs RGB, but the algorithm itself is supposed to generate 16-bit grayscale.  After a lot of headache, I finally found a combo of avenc_ljpeg and avdec_mjpeg that would work to encode and then decode the RGB stream and get the exact same data on both ends.  Now, I would like to do the same for a 16-bit grayscale stream of images, but am having little luck.  avenc_mjpeg does support GRAY16_BE/LE, but I don't know how to make it lossless.

Does such a solution exist, or do we need to roll our own/modify a codec?

Thanks,
Ryan Talbot
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