Decoder 'drain' functionality

[jsorg71]

I'm trying to update from an older libyami and I used the drain parameter of decodeGetOutput. Setting it to true would get me a frame out for every frame in. Since that is removed, how do you get similar functionality?

[xuguangxin]

Hi @jsorg71 ,
you may need call decode with 0 size input to drain the decode.
sample code are here
https://github.com/intel/libyami-utils/blob/master/tests/vppinputdecode.cpp#L86

[jsorg71]

Hi @xhaihao , I think I tried that, I'll try again tomorrow to be sure. It looks like that is used for EOF event where you are about to delete or restart the decoder.

[xuguangxin]

@jsorg71 , if you want one frame in, one frame out. You may need set enableLowLatency. But it has limitation. It only works for h264 and IPPPP pattern. It's a hack mode, we do not strictly follow the spec in this mode.
If possible, I suggest you change your encoder to zero latency mode. It maybe better.

[jsorg71]

@xuguangxin thanks, I'll look into that. I only use I and P frames.
I don't have that option in libyami 1.2.
When I build 1.3 I get

In file included from vaapicontext.cpp:27:0:
../vaapi/vaapistreamable.h: In function ‘std::ostream& operator<<(std::ostream&, const VAEntrypoint&)’:
../vaapi/vaapistreamable.h:108:10: error: ‘VAEntrypointFEI’ was not declared in this scope
     case VAEntrypointFEI:
          ^~~~~~~~~~~~~~~
Makefile:603: recipe for target 'libyami_vaapi_la-vaapicontext.lo' failed

[xuguangxin]

this added by intel/libva@397a4a2, you can comment out the case or you can upgrade libva to a newer version.
It's hard to add #ifdef for every libva version, it will make the code unreadable.

[jsorg71]

@xuguangxin I got 1.3.0 building, thanks. I set 'enableLowLatency' before calling start, but I still don't see any difference.

[jsorg71]

BTW, it looks like the VAEntrypointFEI issue is fixed in HEAD of apache.

[xuguangxin]

@jsorg71 , thanks for information. It may related to bitstream, could you send your bitstream to me.
thanks

[jsorg71]

@xuguangxin Sure, I'll capture and provide I and P frames that work perfectly with libyami 0.3.1 but not with any version after.

[jsorg71]

I put the files in http://server1.xrdp.org/a8/libyami-issue-844/

surface_command_beef_0.bin
h264 frames with a 16 byte header between each frame.
It contains
8 frames at 1920x1080 I P P P ...
42 frames at 424x368 I P P P ...
7 frames at 1032x776 I P P P ...

surface_command_beef_1.bin
h264 frames with a 16 byte header between each frame.
It contains
2 frames at 1920x1080 I P

h264_beef_stepper_031.tar.gz
example program for libyami v0.3.1 that works as expected

h264_beef_stepper_apache.tar.gz
example program for current apache head that I can't seem to get working.

of course, you will have to edit the Makefile to get building for your system but they are really simple.

[xuguangxin]

thanks jsorg71, we will try it.

[xuguangxin]

Hi @jsorg71
Although we need internal test and unit test, could you help try
https://github.com/xuguangxin/libyami-utils/tree/fix_low_latency
https://github.com/xuguangxin/libyami/tree/fix_low_latency
see if it meet your requirement?
You need change two things in your application

1. add low latency flag as you did.
2. add VIDEO_DECODE_BUFFER_FLAG_FRAME_END when you know it's a completed frame. this will tell decoder stop search frame, decode current frame ASAP

Another thing is interlace stream, do you have interlace requirement for low latency?

thanks

[jsorg71]

@xuguangxin Thanks, that works!

[xuguangxin]

glad to hear this.

[jsorg71]

What do you think about making a 1.3.1 release? I like this feature but don't like grabbing a develop branch. It looks like it been about a year.

[jsorg71]

thanks guys

[xuguangxin]

no problem, it's our job

[jsorg71]

release here #864