multiple instances of omxmjpegdec seems not work well

Submitted by Yuji Kuwabara

Description

I'm not sure whether it is a problem of GStreamer or not.
On Raspberry Pi3, multiple instances of omxmjpegdec seems not work well at the same time.

How to reproduce:
Use 2 of separate Terminals and a Photo JPEG movie file.
(I used 640x480 30fps)

On the one Terminal:
gst-launch-1.0 filesrc location=/home/pi/Videos/Fish.mov ! decodebin ! glimagesink

On the other Terminal:
gst-launch-1.0 filesrc location=/home/pi/Videos/Fish.mov ! decodebin ! videocrop bottom=100 ! glimagesink

(NOTE: videocrop is used to show first (background) video)

Result:
These movies are not played well, and many "Frame is too late" messages are shown (GST_DEBUG=2).

omxvideodec gstomxvideodec.c:1387:gst_omx_video_dec_loop:`<omxmjpegdec-omxmjpegdec0>` Frame is too late, dropping

On 1.12.0, same problem was seen.
I saw a message from gst_omx_port_wait_enabled_unlocked() several times,
but since updated to 1.12.2, not yet seen.

Timeout waiting for ... port ... to be enabled

The combination of a Photo JPEG and a H.264 movie files is no problem.
Also, the combination of two H.264 movie files is no problem.
2 instances of omxplayer also works well for same (used in above test) Photo JPEG movie file.

Version: 1.12.2

Admin message