Serial port interface on frame grabber

[vk_gst]

Hi Josh,

Further debugging into this, I realize that using RTP might cause an issue
with timing. So I avoided using the rtph264pay and rtph264depay. Here are
the new commands: 

imx6: gst-launch-1.0 -v videotestsrc pattern=18 !
video/x-raw,width=100,height=50 ! imxvpuenc_h264 bitrate=5 ! h264parse !
filesink location=/dev/ttyUSB1 

PC: CAPS=video/x-h264 
PC:  gst-launch-1.0 -v filesrc location=/dev/ttyUSB1 ! $CAPS ! h264parse !
avdec_h264 ! autovideosink sync=true 

There are no errors observed on the imx6 board. 
However, I see the following errors at the PC side : 
PC:# GST_DEBUG=3 gst-launch-1.0 -v filesrc location=/dev/ttyUSB1 ! $CAPS !
h264parse ! avdec_h264 ! autovideosink sync=true 
 Setting pipeline to PAUSED … 
0:00:00.066439392 15475 0x556d8a01d160 WARN basesrc
gstbasesrc.c:3583:gst_base_src_start_complete: pad not activated yet 
 Pipeline is PREROLLING … 
0:00:21.730466251 15475 0x556d8a000940 WARN capsfilter
gstcapsfilter.c:455:gst_capsfilter_prepare_buf: error: Filter caps do not
completely specify the output format 
 0:00:21.730523691 15475 0x556d8a000940 WARN capsfilter
gstcapsfilter.c:455:gst_capsfilter_prepare_buf: error: Output caps are
unfixed: video/x-h264, width=(int)[ 1, 8192 ], height=(int)[ 1, 8192 ],
framerate=(fraction)[ 0/1, 2147483647/1 ] 
 0:00:21.730676173 15475 0x556d8a000940 WARN basetransform
gstbasetransform.c:2159:default_generate_output: could not get buffer from
pool: error 
 0:00:21.730742223 15475 0x556d8a000940 WARN basesrc
gstbasesrc.c:3055:gst_base_src_loop: error: Internal data stream error. 
 0:00:21.730775478 15475 0x556d8a000940 WARN basesrc
gstbasesrc.c:3055:gst_base_src_loop: error: streaming stopped, reason error
(-5) 
 ERROR: from element /GstPipeline:pipeline0/GstCapsFilter:capsfilter0:
Filter caps do not completely specify the output format 
 Additional debug info: 
 gstcapsfilter.c(455): gst_capsfilter_prepare_buf ():
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0: 
 Output caps are unfixed: video/x-h264, width=(int)[ 1, 8192 ],
height=(int)[ 1, 8192 ], framerate=(fraction)[ 0/1, 2147483647/1 ] 
 ERROR: pipeline doesn’t want to preroll. 
 Setting pipeline to NULL … 
Freeing pipeline … 



The error is related to caps negotiation, which I am not sure how to solve.
Do you have a hand on this? 

Also I want to try and replace the videotestsrc with a camera interface, do
you think this would work?
I am not confident regarding the behaviour of device files in Linux, so I am
not sure, even if writing to a device file and reading it using GStreamer
would work. What are your views on this?



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