I don't know much about video, but to play an h264 encoded file into a screen, don't you have to decode it to something like RGB first? I would expect playing a video that is in RGB format to skip the decoding step, therefore being strictly faster than a video that has to be decoded (even if I decode it with hardware acceleration, as I did). That doesn't seem to be the case, but I can't tell whether that is due to a software issue, like the RGB file being played inefficiently. I must be very wrong about something.
I've been playing around all day with GStreamer trying to smoothly play video files on my Raspberry Pi 3. I finally managed it in an almost fresh install of Jessie (after
apt-get upgrade and
apt-get install gstreamer1.0-tools).
I have an uncompressed (8-bit RGB) .mov version of the video I want to play, and an h264-encoded .mov version. I played both of them:
gst-launch-1.0 filesrc location=h264_test.mov ! qtdemux name=demuxer ! h264parse ! omxh264dec ! ximagesink gst-launch-1.0 filesrc location=uncompressed_test.mov ! qtdemux ! videoparse format=GST_VIDEO_FORMAT_RGB height=800 width=480 ! glimagesink
Honestly, I expected the uncompressed version would play faster, but it's slow. The h264-encoded version, which
omxh264dec decodes with hardware acceleration, plays at the correct speed (which in this case is 25 FPS), but the other one lags and I get GStreamer warnings about buffers being dropped and the computer being slow. I used different sinks for each one (
glimagesink) because neither file would play correctly on the other one, which I'm not sure makes a difference.
I think I would've preferred that the uncompressed version was faster, because that means I don't have to bother with fixing banding issues. Really, though, I'm asking this question because I feel like I have a misconception about how this works.
UPDATE: I tried adding a queue, which I understand should buffer video, thinking that SD card reading was the bottleneck:
gst-launch-1.0 filesrc location=uncompressed_test.mov ! qtdemux ! videoparse format=GST_VIDEO_FORMAT_RGB height=800 width=480 ! queue max-size-bytes=125000000 max-size-time=5000000000 max-size-buffers=1000 ! glimagesink
As far as I can tell, the file is playing just as slowly, and I'm still getting GStreamer warnings. Maybe the OpenGL renderer is slow? I'll script some read speed tests later to see how long exactly it takes to read the file.
The particular file I'm using is 116 MB, 4 seconds long and has a bitrate of 232 Mbps.