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x264enc: Work around a rate control issue in libx264

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When variable framerate is disabled in libx264 (which occurs when using
the zerolatency tuning), libx264 ignores timestamps but still uses the
timebase leading to messed up rate control with our nanosecond timebase.

We work around this issue by setting the timebase to the reciprocal of
the framerate and we validate that the framerate is suitable.

This has been fixed upstream in libx264 but there are non-fixed versions
in the wild so this workaround is still needed.

Fixes bug #632861
This commit is contained in:
Robert Swain 2010-10-22 11:29:55 +02:00
parent 0fa75d404b
commit 6f2db739ae
1 changed files with 19 additions and 1 deletions
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20
ext/x264/gstx264enc.c
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@ -346,7 +346,7 @@ static const GFlagsValue tune_types[] = {
{0x0, "No tuning", "none"}, {0x0, "No tuning", "none"},
{0x1, "Still image", "stillimage"}, {0x1, "Still image", "stillimage"},
{0x2, "Fast decode", "fastdecode"}, {0x2, "Fast decode", "fastdecode"},
{0x4, "Zero latency", "zerolatency"}, {0x4, "Zero latency (requires constant framerate)", "zerolatency"},
{0, NULL, NULL}, {0, NULL, NULL},
}; };
@ -1159,6 +1159,24 @@ gst_x264_enc_init_encoder (GstX264Enc * encoder)
break; break;
} }
#if X264_BUILD >= 81 && X264_BUILD < 106
/* When vfr is disabled, libx264 ignores buffer timestamps. This causes
* issues with rate control in libx264 with our nanosecond timebase. This
* has been fixed upstream in libx264 but this workaround is required for
* pre-fix versions. */
if (!encoder->x264param.b_vfr_input) {
if (encoder->x264param.i_fps_num == 0) {
GST_ELEMENT_ERROR (encoder, STREAM, ENCODE,
("Constant framerate is required."),
("The framerate caps (%d/%d) indicate VFR but VFR is disabled in libx264. (Is the zerolatency tuning in use?)",
encoder->x264param.i_fps_num, encoder->x264param.i_fps_den));
return FALSE;
}
encoder->x264param.i_timebase_num = encoder->x264param.i_fps_den;
encoder->x264param.i_timebase_den = encoder->x264param.i_fps_num;
}
#endif
#ifdef X264_PRESETS #ifdef X264_PRESETS
if (encoder->profile if (encoder->profile
&& x264_param_apply_profile (&encoder->x264param, && x264_param_apply_profile (&encoder->x264param,