H.264 encoded video has data distortion at the start of file.

[Ashish Kumar Mishra]

Hi All ,

I am working with v4l2src + alsasrc , the application ( Linux Gstreamer application) creates multiple files of user defined chunk

The basic logic of the same could be mapped to :-
gst-launch-1.0 -v v4l2src do-timestamp=true ! video/x-raw,width=960,height=720,framerate=30/1 ! timeoverlay shaded-background=1 ! x264enc tune=zerolatency ! mux. alsasrc ! audio/x-raw,width=16,depth=16,rate=44100,channels=2 ! queue ! mux. matroskamux name=mux  ! filesink

The files has some quality issue ( Attached is the snapshot ) at the start of every file created
Basic google search pointed to some problems in H.264 frame

Could team member please provide some pointers as to how could this problem be addressed.
The video is proper after 3-4sec in every file.

Thanks
Ashish Kumar Mishra

[Chuck Crisler-3]

The h.264 decoder needs a complete reference frame to properly decode a stream. That includes an SPS, PPS and an IFrame. Probably you are writing data to the file that doesn't start with this data. You should delay the file write until you have these elements. Often they are transmitted in that order. However, some IP sources will only transmit the SPS and PPS once and some may never transmit them in band, only in an SDP. So you need to be careful depending on the source and encoder. GSTREAMER elements do have properties to force re-transmitting those elements.

On Feb 12, 2016 4:55 AM, "Ashish Kumar Mishra" <[hidden email]> wrote:

Hi All ,

I am working with v4l2src + alsasrc , the application creates multiple files
of user defined chunk
The basic logic of the could be mapped to :-
*gst-launch-1.0 -v v4l2src do-timestamp=true !
video/x-raw,width=960,height=720,framerate=30/1 ! timeoverlay
shaded-background=1 ! x264enc tune=zerolatency ! mux. alsasrc !
audio/x-raw,width=16,depth=16,rate=44100,channels=2 ! queue ! mux.
matroskamux name=mux  ! filesink *

The files has some quality issue at the start of every file created
,attached is the snapshot of the same.
Basic google search pointed to some problems in H.264 frame .

Could team member please provide some pointers as to how could this problem
be addressed.
The video is proper after 3-4sec in every file.

Thanks
Ashish Kumar Mishra

<http://gstreamer-devel.966125.n4.nabble.com/file/n4675812/38.png>



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[Ashish Kumar Mishra]

Hi Chuck Crisler-3 ,

1) I have created an dynamic pipeline to create multiple ".mkv" file of user defined duration.

2) " ....You should delay the file write until you have these elements..."
In the current implementation , after the user defined time the pads are paused , new file is created and the pads are re-started again. Now in this case i have no mechanism to know if all the required frames has arrived at the time of file creation.

Could you please provide some pointers as to how can delay the file write till all the required frames are received  ?  i.e how to determine & ensure all the frames are received ?
( I don't in-depth information of Gstreamer , this is the first project on Gstreamer application side.
  Hence it would be helpful if you could share any sample snippet of code .)

Roughly the pipeline has the below mentioned skeleton  ( actual implementation is in C code )
gst-launch-1.0 -v v4l2src ! video/x-raw,width=960,height=720,framerate=30/1 ! x264enc ! mux. alsasrc ! audio/x-raw,width=16,depth=16,rate=44100,channels=2 ! mux. avimux name=mux ! filesink location=test.avi


Thanks
Ashish Kumar Mishra.

[Ashish Kumar Mishra]

Hi Group Members ,
Could any one please share some pointers as to how this could be addressed or any sample code / explanation on the same.

Thanks ,
Ashish Kumar Mishra

[Ashish Kumar Mishra]

Hi Group members ,

Could group member's please provide any inputs as to how can we configure pipeline to get the "re-transmission " of
SPS / PPS / IFrame ?

I would be thankful if group members could share any web link / tutorial any other ways to understand the
basic details of these frames and there roles / importance.

As of now i am using below mentioned links to have some understanding for H.264

http://update.websamsung.net/OnlineTutorial/MPcamera/HTML_EN/contents/pcMenu01.html
http://update.websamsung.net/OnlineTutorial/MPcamera/HTML_EN/contents/pcMenu02.html
and
http://gentlelogic.blogspot.in/2011/11/exploring-h264-part-2-h264-bitstream.html 

Thanks ,
Ashish Kumar Mishra.

[Sebastian Dröge-3]

On Do, 2016-03-03 at 21:15 -0800, Ashish Kumar Mishra wrote:
> Hi Group members , 
>
> Could group member's please provide any inputs as to how can we configure
> pipeline to get the "re-transmission " of SPS / PPS / IFrame ?

If your encoder supports that (x264enc does), you can send a force-
keyunit event. See gst_video_event_new_upstream_force_key_unit().

--
Sebastian Dröge, Centricular Ltd · http://www.centricular.com

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