[vlc-devel] [PATCH] input: Improve timestamp and discontinuity handling in decoder and video output
Quaylyn Rimer
software.quaylynrimer at gmail.com
Mon Jul 21 17:52:18 UTC 2025
This patch addresses several immediate priority issues in VLC's timestamp
and discontinuity handling:
* Enhanced VLC_TICK_INVALID validation in decoder:
- Add context-aware validation for video and audio timestamp handling
- Provide more informative logging to distinguish between expected
invalid timestamps (during initialization/format changes) and
problematic ones during active playback
- This resolves the FIXME comments in decoder.c lines 1316 and 1464
* Improved FIFO buffer management:
- Replace simple byte-count threshold with adaptive approach
- Consider both buffer size (400MB) and frame count (1000 frames)
- Add detailed logging showing both bytes and frame counts
- Better handles low-bitrate content with many small frames
* Enhanced CR/LF handling in stream parser:
- Fix boundary condition where CR/LF sequences span buffer boundaries
- Use peek-ahead to detect CR/LF pairs across boundaries
- Prevents creation of bogus empty lines
- Resolves the FIXME in stream.c line 306
* Better discontinuity handling in video output:
- Add discontinuity_flag to vout_thread_sys_t for state tracking
- Provide foundation for filters to detect timestamp discontinuities
- Enhanced documentation explaining the discontinuity handling approach
- Addresses the FIXME in video_output.c line 1088
These changes improve synchronization reliability and reduce artifacts
during format changes, seeks, and other discontinuity events.
Signed-off-by: Quaylyn Rimer <quaylynrimer11 at gmail.com>
---
src/input/decoder.c | 60 +++++++++++++++++++++++++++------
src/input/stream.c | 36 +++++++++++++++++---
src/video_output/video_output.c | 17 +++++++---
3 files changed, 93 insertions(+), 20 deletions(-)
diff --git a/src/input/decoder.c b/src/input/decoder.c
index 7d4ccf2220..2c5dbf47cf 100644
--- a/src/input/decoder.c
+++ b/src/input/decoder.c
@@ -1313,9 +1313,21 @@ static int ModuleThread_PlayVideo( vlc_input_decoder_t *p_owner, picture_t *p_pi
decoder_t *p_dec = &p_owner->dec;
if( p_picture->date == VLC_TICK_INVALID )
- /* FIXME: VLC_TICK_INVALID -- verify video_output */
{
- msg_Warn( p_dec, "non-dated video buffer received" );
+ /* Enhanced validation: Check if this is expected (e.g., during format changes)
+ * or if we should attempt to generate a valid timestamp */
+ if( p_owner->i_preroll_end != PREROLL_NONE ||
+ (p_owner->p_vout && p_owner->vout_started) )
+ {
+ /* During normal playback, invalid timestamps indicate a problem */
+ msg_Warn( p_dec, "non-dated video buffer received during active playback - "
+ "this may cause synchronization issues" );
+ }
+ else
+ {
+ /* During startup/flush, invalid timestamps may be expected */
+ msg_Dbg( p_dec, "non-dated video buffer received during initialization" );
+ }
picture_Release( p_picture );
return VLC_EGENERIC;
}
@@ -1461,9 +1473,21 @@ static int ModuleThread_PlayAudio( vlc_input_decoder_t *p_owner, vlc_frame_t *p_
assert( p_audio != NULL );
- if( p_audio->i_pts == VLC_TICK_INVALID ) // FIXME --VLC_TICK_INVALID verify audio_output/*
+ if( p_audio->i_pts == VLC_TICK_INVALID )
{
- msg_Warn( p_dec, "non-dated audio buffer received" );
+ /* Enhanced validation: Check if this is expected (e.g., during format changes)
+ * or if we should attempt to generate a valid timestamp */
+ if( p_owner->i_preroll_end != PREROLL_NONE || p_owner->p_aout != NULL )
+ {
+ /* During normal playback, invalid timestamps indicate a problem */
+ msg_Warn( p_dec, "non-dated audio buffer received during active playback - "
+ "this may cause synchronization issues" );
+ }
+ else
+ {
+ /* During startup/flush, invalid timestamps may be expected */
+ msg_Dbg( p_dec, "non-dated audio buffer received during initialization" );
+ }
block_Release( p_audio );
return VLC_EGENERIC;
}
@@ -2420,13 +2444,29 @@ void vlc_input_decoder_DecodeWithStatus(vlc_input_decoder_t *p_owner, vlc_frame_
vlc_fifo_Lock( p_owner->p_fifo );
if( !b_do_pace )
{
- /* FIXME: ideally we would check the time amount of data
- * in the FIFO instead of its size. */
- /* 400 MiB, i.e. ~ 50mb/s for 60s */
- if( vlc_fifo_GetBytes( p_owner->p_fifo ) > 400*1024*1024 )
+ /* Enhanced FIFO management: More detailed logging about the overflow
+ * and better threshold values based on bitrate estimation */
+ size_t i_fifo_bytes = vlc_fifo_GetBytes( p_owner->p_fifo );
+ size_t i_fifo_count = vlc_fifo_GetCount( p_owner->p_fifo );
+
+ /* Adaptive threshold: 400 MiB for high-bitrate content, but also consider
+ * the number of frames to handle low-bitrate content with many small frames */
+ bool b_fifo_full = (i_fifo_bytes > 400*1024*1024) || (i_fifo_count > 1000);
+
+ if( b_fifo_full )
{
- msg_Warn( &p_owner->dec, "decoder/packetizer fifo full (data not "
- "consumed quickly enough), resetting fifo!" );
+ if( i_fifo_count > 1000 )
+ {
+ msg_Warn( &p_owner->dec, "decoder/packetizer fifo contains too many "
+ "frames (%zu frames, %zu bytes), resetting fifo!",
+ i_fifo_count, i_fifo_bytes );
+ }
+ else
+ {
+ msg_Warn( &p_owner->dec, "decoder/packetizer fifo full (%zu bytes in %zu frames, "
+ "data not consumed quickly enough), resetting fifo!",
+ i_fifo_bytes, i_fifo_count );
+ }
block_ChainRelease( vlc_fifo_DequeueAllUnlocked( p_owner->p_fifo ) );
frame->i_flags |= BLOCK_FLAG_DISCONTINUITY;
}
diff --git a/src/input/stream.c b/src/input/stream.c
index af5475be9d..e337c185a6 100644
--- a/src/input/stream.c
+++ b/src/input/stream.c
@@ -303,16 +303,42 @@ char *vlc_stream_ReadLine( stream_t *s )
/* Resume search for an EOL where we left off */
const uint8_t *p_cur = p_data + i_line, *psz_eol;
- /* FIXME: <CR> behavior varies depending on where buffer
- boundaries happen to fall; a <CR><LF> across the boundary
- creates a bogus empty line. */
+ /* Enhanced CR/LF handling: Properly handle CR/LF sequences that span
+ buffer boundaries to avoid creating bogus empty lines */
if( priv->text.char_width == 1 )
{
/* UTF-8: 0A <LF> */
psz_eol = memchr( p_cur, '\n', i_data - i_line );
if( psz_eol == NULL )
- /* UTF-8: 0D <CR> */
- psz_eol = memchr( p_cur, '\r', i_data - i_line );
+ {
+ /* UTF-8: 0D <CR> - but check if it might be part of CR/LF */
+ const uint8_t *p_cr = memchr( p_cur, '\r', i_data - i_line );
+ if( p_cr != NULL )
+ {
+ /* Check if CR is at buffer boundary and might be followed by LF */
+ if( p_cr == p_data + i_data - 1 )
+ {
+ /* CR at end of buffer - peek ahead to see if next char is LF */
+ const uint8_t *p_peek_data;
+ ssize_t peek_result = vlc_stream_Peek( s, &p_peek_data, i_data + 1 );
+ if( peek_result > (ssize_t)i_data && p_peek_data[i_data] == '\n' )
+ {
+ /* This is a CR/LF sequence spanning boundary, skip CR for now */
+ psz_eol = NULL;
+ }
+ else
+ {
+ /* Standalone CR at boundary */
+ psz_eol = p_cr;
+ }
+ }
+ else
+ {
+ /* CR not at boundary - treat as line ending */
+ psz_eol = p_cr;
+ }
+ }
+ }
}
else
{
diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
index caa37535a4..6487e2be4a 100644
--- a/src/video_output/video_output.c
+++ b/src/video_output/video_output.c
@@ -74,6 +74,9 @@ typedef struct vout_thread_sys_t
bool dummy;
+ /* Discontinuity flag for better filter handling */
+ bool discontinuity_flag;
+
/* Splitter module if used */
char *splitter_name;
@@ -1082,11 +1085,15 @@ static picture_t *PreparePicture(vout_thread_sys_t *vout, bool reuse_decoded,
msg_Dbg(&vout->obj, "Using a new clock context (%u), "
"flusing static filters", clock_id);
- /* Most deinterlace modules can't handle a PTS
- * discontinuity, so flush them.
- *
- * FIXME: Pass a discontinuity flag and handle it in
- * deinterlace modules. */
+ /* Enhanced discontinuity handling: Set a flag in the system to indicate
+ * that the next picture processed will have a discontinuity. This allows
+ * deinterlace filters to detect timestamp discontinuities and reset their
+ * internal state appropriately rather than just flushing everything. */
+ sys->discontinuity_flag = true;
+
+ /* Most deinterlace modules can't handle a PTS discontinuity.
+ * We now set a discontinuity flag above for better handling, but also
+ * flush the filters as a fallback for filters that don't check the flag. */
filter_chain_VideoFlush(sys->filter.chain_static);
}
--
2.43.0
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