Inconsistent x264enc in 1.1.4

Wed Sep 18 02:54:52 PDT 2013

Hi

I have discovered some "features" of h.264 pipelines in Gstreamer 1.1.4,
which I didn't see in earlier versions. I'll try to describe it below.

In the following we set the following environment variable

RAWVIDEO='video/x-raw, bpp=(int)32, depth=(int)32, endianness=(int)4321,
format=(string)BGRA, red_mask=(int)65280, green_mask=(int)16711680,
blue_mask=(int)-16777216, width=(int)1280, height=(int)720,
framerate=(fraction)25/1, pixel-aspect-ratio=(fraction)1/1,
interlaced=(boolean)false'

Now we run the following pipeline to see all works fine.

gst-launch-1.0 -v videotestsrc is-live=true !\
    $RAWVIDEO !\
    videoconvert !\
    x264enc tune=zerolatency !\
    fakesink

All though it works, the similar pipeline for gstreamer-0.10 would encode
main profile level 3.1 H.264 stream based on I420 input. Now with 1.1.4 the
pipeline will by default for this setup encode the profile high-4:4:4,
which is quite different. This is quite unexpected, but technically it may
not be considered an error, but rather an annoyance. However it is a
complexity that for sure will generate some problems for many because
high-4:4:4 will not be supported on many players. High-4:4:4 is a rather
advanced and complex little used (in the past) format. Furthermore, it is a
bit unclear which high-4:4:4 profile this actually is, but more on that
later.

Anyway if we tell the pipeline that we want a main profile, we can do it
like this:

gst-launch-1.0 -v videotestsrc is-live=true !\
    $RAWVIDEO !\
    videoconvert !\
    x264enc tune=zerolatency !\
    'video/x-h264, profile=(string)main' !\
    fakesink

However that result in the following error messages

x264 [error]: main profile doesn't support 4:4:4
Redistribute latency...
/GstPipeline:pipeline0/GstX264Enc:x264enc0.GstPad:src: caps = video/x-h264,
codec_data=(buffer)01f4001fffe1001a67f4001f91964014016ec044000003000400000300ca3c60c92001000668ebcc448440,
stream-format=(string)avc, alignment=(string)au, level=(string)3.1,
profile=(string)high-4:4:4, width=(int)1280, height=(int)720,
pixel-aspect-ratio=(fraction)1/1, framerate=(fraction)25/1
ERROR: from element /GstPipeline:pipeline0/GstVideoTestSrc:videotestsrc0:
Internal data flow error.
Additional debug info:
gstbasesrc.c(2857): gst_base_src_loop ():
/GstPipeline:pipeline0/GstVideoTestSrc:videotestsrc0:
streaming task paused, reason not-negotiated (-4)

Funny. In the previous example it used 4:4:4 successfully. But I assume it
insist on 4:4:4 and want to combine this with main profile. Main-4:4:4 is
not a profile. Ok, I suspect that the encoder fails to tell videoconvert
properly what it can use for input, so lets help it a bit by asking for a
I420 input. It OUGHT not be necessary, but lets help it anyway.

gst-launch-1.0 -v videotestsrc is-live=true !\
    $RAWVIDEO !\
    videoconvert !\
    'video/x-raw, format=(string)I420' !\
    x264enc tune=zerolatency !\
    'video/x-h264, profile=(string)main' !\
    fakesink

Now that actually works, and we get a nice H.264 main profile stream
generated from input converted to I420 but I believe the x264enc should
have reached that conclusion by it self. If GStreamer gets too many
plugins, that can't figure out to request the right input, I fear it will
over time grow too complex to use for most.

Furthermore, it appear that x264enc uses the word high profile at little
bit to carelessly. High Profile and 4:4:4 is many things and for the future
we need to be very precise in using these terms. To me at least, it was
very unclear which high-4:4:4 profile it claimed it was using successfully
and which high-4:4:4 it said it did not support. As such I think letting
'profile=high-4:4:4' cover both Hi444PP and Hi444IP and possibly more (if
that is what it is doing) is asking for troubles.

Kind regards
Peter Maersk-Moller

For your convenience, I here reprint an extract from wikipedia:
High Profile (HiP)The primary profile for broadcast and disc storage
applications, particularly for high-definition television applications (for
example, this is the profile adopted by the Blu-ray
Disc<http://en.wikipedia.org/wiki/Blu-ray_Disc>storage format and the
DVB <http://en.wikipedia.org/wiki/Digital_Video_Broadcasting> HDTV
broadcast service).Progressive High Profile (PHiP)Similar to the High
profile, but without support of field coding features.Constrained High
ProfileSimilar to the Progressive High profile, but without support of B
(bi-predictive) slices.High 10 Profile (Hi10P)Going beyond typical
mainstream consumer product capabilities, this profile builds on top of the
High Profile, adding support for up to 10 bits per sample of decoded
picture precision.High 4:2:2 Profile (Hi422P)Primarily targeting
professional applications that use interlaced video, this profile builds on
top of the High 10 Profile, adding support for the 4:2:2 chroma
subsampling<http://en.wikipedia.org/wiki/Chroma_subsampling>format
while using up to 10 bits per sample of decoded picture precision.High
4:4:4 Predictive Profile (Hi444PP)This profile builds on top of the High
4:2:2 Profile, supporting up to 4:4:4 chroma sampling, up to 14 bits per
sample, and additionally supporting efficient lossless region coding and
the coding of each picture as three separate color planes.

For camcorders, editing, and professional applications, the standard
contains four additional
Intra-frame<http://en.wikipedia.org/wiki/Intra-frame>-only
profiles, which are defined as simple subsets of other corresponding
profiles. These are mostly for professional (e.g., camera and editing
system) applications:
High 10 Intra ProfileThe High 10 Profile constrained to all-Intra use.High
4:2:2 Intra ProfileThe High 4:2:2 Profile constrained to all-Intra use.High
4:4:4 Intra ProfileThe High 4:4:4 Profile constrained to all-Intra use.CAVLC
4:4:4 Intra Profile
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