[vlc-devel] commit: input: Add --auto-adjust-pts-delay, this allows to stream/ receive with an extremely low latency. (Pierre d'Herbemont )
git version control
git at videolan.org
Fri Jun 6 00:13:28 CEST 2008
vlc | branch: master | Pierre d'Herbemont <pdherbemont at videolan.org> | Fri Jun 6 00:13:27 2008 +0200| [ea89b9c2d9d5b13c28da56f6b5ec284614db491f]
input: Add --auto-adjust-pts-delay, this allows to stream/receive with an extremely low latency.
Simple demo:
vlc --sout="#duplicate{dst=display,dst='transcode{vcodec=mp4v}:std{access=http,dst=0.0.0.0:8080,mux=ts}'}" --ignore-config --use-stream-immediate movie.avi &
vlc --use-stream-immediate http://127.0.0.1:8080
and
vlc --use-stream-immediate http://127.0.0.1:8080 --auto-adjust-pts-delay
You'll have to wait a bit until the pts delay is auto adjusted. Generally it takes 2-4 seconds, because access set a very high default pts delay value. One amelioration would be to lower the pts_delay when this option is set to allow a quicker convergence.
The general algorithm requires some tuning, but results are here.
Note, this only works if there is a video track. A similar function could be developped for the audio tracks.
> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=ea89b9c2d9d5b13c28da56f6b5ec284614db491f
---
src/input/decoder.c | 93 ++++++++++++++++++++++++++++++++++++++++++++
src/input/input_internal.h | 7 +++
src/input/var.c | 3 +
src/libvlc-module.c | 2 +
4 files changed, 105 insertions(+), 0 deletions(-)
diff --git a/src/input/decoder.c b/src/input/decoder.c
index ddf6688..ce171b8 100644
--- a/src/input/decoder.c
+++ b/src/input/decoder.c
@@ -726,6 +726,96 @@ static void VoutFlushPicture( vout_thread_t *p_vout )
}
vlc_mutex_unlock( &p_vout->picture_lock );
}
+
+
+static void optimize_video_pts( decoder_t *p_dec )
+{
+ picture_t * oldest_pict = NULL;
+ picture_t * youngest_pict = NULL;
+ int i;
+
+ input_thread_t * p_input = p_dec->p_owner->p_input;
+ vout_thread_t * p_vout = p_dec->p_owner->p_vout;
+ input_thread_private_t * p_priv = p_input->p;
+
+ if( !p_priv->pts_adjust.auto_adjust ) return;
+
+ for( i = 0; i < I_RENDERPICTURES; i++ )
+ {
+ picture_t * pic = PP_RENDERPICTURE[i];
+ if( pic->i_status != READY_PICTURE )
+ continue;
+
+ if( !oldest_pict || pic->date < oldest_pict->date )
+ oldest_pict = pic;
+ if( !youngest_pict || pic->date > youngest_pict->date )
+ youngest_pict = pic;
+ }
+
+ if( !youngest_pict || !oldest_pict )
+ return;
+
+ /* Try to find if we can reduce the pts
+ * This first draft is way to simple, and we can't say if the
+ * algo will converge. It's also full of constants.
+ * But this simple algo allows to reduce the latency
+ * to the minimum. */
+ mtime_t buffer_size = youngest_pict->date - oldest_pict->date;
+ int64_t pts_slide = 0;
+ if( buffer_size < 10000 )
+ {
+ if( p_priv->pts_adjust.i_num_faulty > 10 )
+ {
+ pts_slide = __MAX(p_input->i_pts_delay *3 / 2, 10000);
+ p_priv->pts_adjust.i_num_faulty = 0;
+ }
+ if( p_priv->pts_adjust.to_high )
+ {
+ p_priv->pts_adjust.to_high = !p_priv->pts_adjust.to_high;
+ p_priv->pts_adjust.i_num_faulty = 0;
+ }
+ p_priv->pts_adjust.i_num_faulty++;
+ }
+ else if( buffer_size > 100000 )
+ {
+ if( p_priv->pts_adjust.i_num_faulty > 25 )
+ {
+ pts_slide = -buffer_size/2;
+ p_priv->pts_adjust.i_num_faulty = 0;
+ }
+ if( p_priv->pts_adjust.to_high )
+ {
+ p_priv->pts_adjust.to_high = !p_priv->pts_adjust.to_high;
+ p_priv->pts_adjust.i_num_faulty = 0;
+ }
+ p_priv->pts_adjust.i_num_faulty++;
+ }
+ if( pts_slide )
+ {
+ mtime_t origi_delay = p_input->i_pts_delay;
+
+ p_input->i_pts_delay += pts_slide;
+
+ /* Don't play with the pts delay for more than -2<->3sec */
+ if( p_input->i_pts_delay < -2000000 )
+ p_input->i_pts_delay = -2000000;
+ else if( p_input->i_pts_delay > 3000000 )
+ p_input->i_pts_delay = 3000000;
+ pts_slide = p_input->i_pts_delay - origi_delay;
+
+ msg_Dbg( p_input, "Sliding the pts by %dms pts delay at %dms picture buffer was %dms",
+ (int)pts_slide/1000, (int)p_input->i_pts_delay/1000, (int)buffer_size/1000);
+
+ vlc_mutex_lock( &p_vout->picture_lock );
+ /* Slide all the picture */
+ for( i = 0; i < I_RENDERPICTURES; i++ )
+ PP_RENDERPICTURE[i]->date += pts_slide;
+ /* FIXME: slide aout/spu */
+ vlc_mutex_unlock( &p_vout->picture_lock );
+
+ }
+}
+
static void DecoderDecodeVideo( decoder_t *p_dec, block_t *p_block )
{
input_thread_t *p_input = p_dec->p_owner->p_input;
@@ -757,6 +847,9 @@ static void DecoderDecodeVideo( decoder_t *p_dec, block_t *p_block )
vout_DatePicture( p_dec->p_owner->p_vout, p_pic,
p_pic->date );
+
+ optimize_video_pts( p_dec );
+
vout_DisplayPicture( p_dec->p_owner->p_vout, p_pic );
}
}
diff --git a/src/input/input_internal.h b/src/input/input_internal.h
index dfa59b6..da57642 100644
--- a/src/input/input_internal.h
+++ b/src/input/input_internal.h
@@ -112,6 +112,13 @@ struct input_thread_private_t
int i_slave;
input_source_t **slave;
+ /* pts delay fixup */
+ struct {
+ int i_num_faulty;
+ bool to_high;
+ bool auto_adjust;
+ } pts_adjust;
+
/* Stats counters */
struct {
counter_t *p_read_packets;
diff --git a/src/input/var.c b/src/input/var.c
index 28b4d75..b260107 100644
--- a/src/input/var.c
+++ b/src/input/var.c
@@ -165,6 +165,9 @@ void input_ControlVarInit ( input_thread_t *p_input )
var_Change( p_input, "spu-delay", VLC_VAR_SETVALUE, &val, NULL );
ADD_CALLBACK( "spu-delay", EsDelayCallback );
+ p_input->p->pts_adjust.auto_adjust = var_CreateGetBool(
+ p_input, "auto-adjust-pts-delay" );
+
/* Video ES */
var_Create( p_input, "video-es", VLC_VAR_INTEGER | VLC_VAR_HASCHOICE );
text.psz_string = _("Video Track");
diff --git a/src/libvlc-module.c b/src/libvlc-module.c
index 2373f69..f302c3f 100644
--- a/src/libvlc-module.c
+++ b/src/libvlc-module.c
@@ -1822,6 +1822,8 @@ vlc_module_begin();
add_bool( "use-stream-immediate", false, NULL,
USE_STREAM_IMMEDIATE, USE_STREAM_IMMEDIATE_LONGTEXT, false );
+ add_bool( "auto-adjust-pts-delay", false, NULL,
+ "auto-adjust-pts-delay", "auto-adjust-pts-delay", false );
#if !defined(__APPLE__) && !defined(SYS_BEOS) && defined(LIBVLC_USE_PTHREAD)
add_bool( "rt-priority", false, NULL, RT_PRIORITY_TEXT,
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