Hi,
adds a new variant to the -force_key_frames option "source_no_drop" to make sure
whenever a key frame in the source is dropped, we choose the next frame in the
output stream as a key frame.
-Thilo
From b37c854e7d48b538537b2c9c5e9651ba2ead3e52 Mon Sep 17 00:00:00 2001
From: Keyun Tong <kt...@fb.com>
Date: Sun, 20 Jun 2021 21:42:29 +0200
Subject: [PATCH] fftools/ffmpeg: Add new variant source_no_drop to the
force_key_frames option
Suggested-By: ffm...@fb.com
---
doc/ffmpeg.texi | 7 +++++++
fftools/ffmpeg.c | 6 ++++++
fftools/ffmpeg.h | 1 +
3 files changed, 14 insertions(+)
diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index 9feabe6..ab98a5c 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -996,6 +996,7 @@ Deprecated see -bsf
@item -force_key_frames[:@var{stream_specifier}] @var{time}[,@var{time}...]
(@emph{output,per-stream})
@item -force_key_frames[:@var{stream_specifier}] expr:@var{expr}
(@emph{output,per-stream})
@item -force_key_frames[:@var{stream_specifier}] source
(@emph{output,per-stream})
+@item -force_key_frames[:@var{stream_specifier}] source_no_drop
(@emph{output,per-stream})
@var{force_key_frames} can take arguments of the following form:
@@ -1057,6 +1058,12 @@ starting from second 13:
If the argument is @code{source}, ffmpeg will force a key frame if
the current frame being encoded is marked as a key frame in its source.
+@item source_no_drop
+If the argument is @code{source_no_drop}, ffmpeg will force a key frame if
+the current frame being encoded is marked as a key frame in its source.
+In cases where this particular source frame has to be dropped,
+enforce the next available frame to become a key frame instead.
+
@end table
Note that forcing too many keyframes is very harmful for the lookahead
diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 04ddc9e..57c46e4 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -1287,6 +1287,7 @@ static void do_video_out(OutputFile *of,
}
}
ost->last_dropped = nb_frames == nb0_frames && next_picture;
+ ost->dropped_keyframe = ost->last_dropped && next_picture &&
next_picture->key_frame;
/* duplicates frame if needed */
for (i = 0; i < nb_frames; i++) {
@@ -1347,6 +1348,11 @@ static void do_video_out(OutputFile *of,
&& in_picture->key_frame==1
&& !i) {
forced_keyframe = 1;
+ } else if ( ost->forced_keyframes
+ && !strncmp(ost->forced_keyframes, "source_no_drop", 6)
+ && !i) {
+ forced_keyframe = (in_picture->key_frame == 1) ||
ost->dropped_keyframe;
+ ost->dropped_keyframe = 0;
}
if (forced_keyframe) {
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index e9d30fb..3cfb4c4 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -504,6 +504,7 @@ typedef struct OutputStream {
char *forced_keyframes;
AVExpr *forced_keyframes_pexpr;
double forced_keyframes_expr_const_values[FKF_NB];
+ int dropped_keyframe;
/* audio only */
int *audio_channels_map; /* list of the channels id to pick
from the source stream */
--
1.8.3.2
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