more questions

[James]

> On 24 Apr 2021, at 5:16 pm, Tim-Philipp Müller via gstreamer-devel <gstreamer-devel at lists.freedesktop.org> wrote:
> 
> On Sat, 2021-04-24 at 15:18 +0800, James via gstreamer-devel wrote:
> 
> Hi,
> 
>> Learning but still lots to go.
>> 
>> I have a test pipeline
>> 
>> gst-launch-1.0 -t v4l2src name=source device=/dev/video2 ! \
>>             video/x-h264,width=1920,height=1080,framerate=30/1 ! \
>>             h264parse ! queue ! avdec_h264 ! \
>>             autovideosink
>> 
>> 
>> I coded that as
>> 
>>         pipeline = gst_parse_launch ("v4l2src name=source ! "
>>             "video/x-h264,width=1920,height=1080,framerate=30/1 ! "
>>             "h264parse ! queue ! avdec_h264 ! autovideosink", NULL);
>> 
>> The two do not yield the same result, in particular the gst-launch
>> does feedback 1920x1080 to the card.
>> The compiled code does not, so the card stays in its native 720x576
>> resolution.
>> 
>> What and why
>> 
>> https://gstreamer.freedesktop.org/documentation/tools/gst-
>> launch.html?gi-language=c
>> 
>> says -o file, but that option does not exist. How can I find what
>> parse did to make a pipeline
> 
> gst-launch uses gst_parse_launch() so it should behave the same.
> 
> Your gst-launch pipeline has an additional device=/dev/video2 though?

Tim ta

       g_object_set (source, "device", argv[1], NULL);


but in particular gst-launch passes the resolution back to the card, the compiled pipeline does not.
gst-launch does that too (not pass back) if the CAPS are further down the line, ie other elements do not pass caps back. 
So if parse-launch () does not do it correctly what does parse-launch () actuallly do (read the source, Luke)  but how to see the pipeline that it makes. Maybe spelunking -v

James
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