[gst-devel] [gst-cvs] wtay gst-plugins-good: gst-plugins-good/gst-plugins-good/gst/rtp/
waiming at ailuropoda.net
Wed Dec 12 14:25:24 CET 2007
On Wed, 2007-12-12 at 10:28 +0100, Peter Kjellerstedt wrote:
> > Patch by: Wai-Ming Ho <webregbox at yahoo dot co dot uk>
> > * gst/rtp/gstrtph264pay.c: (gst_rtp_h264_pay_init),
> > (gst_rtp_h264_pay_finalize), (gst_rtp_h264_pay_setcaps),
> > (next_start_code), (is_nal_equal), (gst_rtp_h264_pay_decode_nal),
> > (encode_base64), (gst_rtp_h264_pay_parse_sps_pps),
> > (gst_rtp_h264_pay_handle_buffer):
> > * gst/rtp/gstrtph264pay.h:
> > Use higher performance start-code searching.
> > Parse NALs and store SPS, PPS and profile in the caps so that they can
> > be used in the SDP. Fixes #502814.
> > Modified files:
> > . : ChangeLog
> > gst/rtp : gstrtph264pay.c gstrtph264pay.h
> > Links:
> * In gst_rtp_h264_pay_finalize():
> Why check for NULL before calling g_free()?
> * In encode_base64():
> Why implement yet another base64-encoder? Now there is one
> in the RTSP-code and one here. Wouldn't it make sense to have
> one implementation for all of GStreamer? And if glib >= 2.12
> then I guess you could use g_base64_encode(), and not need
> to have any at all.
Pls check with Wim Taymans. The original patch proposed on Bugzilla uses
> * Why whould is_nal_equal() be faster than memcmp()?
> On what architectures?
> Oh, and the comment preceding it mentions memcpy rather
> than memcmp()...
fingers typing error :-) it's suppose to read memcmp()
I tested it on Ubuntu 7.04 /Intel Genuine Intel(R) CPU 2140 @ 1.60GHz
stepping 02. when I proposed the patch, is_nal_equal() is either the
patched implementation or a simple call to memcmp().
As for why, I would have to look at the gcc generated code but a quick
guess would be the 32-bit XOR's instead of byte-wise CMP (since memcmp()
needs to return either equal, less or greater).
Other than that, if the code is not critical performance hit, I would be
pretty happy if it was a simple call to memcmp(). The gain of 20% is
observed only when both blocks are identical most (or all in the case os
single SPS/PPS H264 bitstreams) of the time.
> * Why not make gst_rtp_h264_pay_decode_nal() return a gboolean
> denoting the updated status, rather than making it take a
> gboolean return parameter?
That would be a good idea.
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