[FFmpeg-devel] [PR] fftools/ffmpeg_demux: Fix readrate sleep calculation (PR #21386)

[desmondliu via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21386 opened by desmondliu
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21386
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21386.patch

Calculation of max_pts and limit_pts may overflow because adding
(int64_t + int64_t + float) results in a float that easily
overflows. This can trigger a very long av_usleep().


>From aec3a8741e2304f4e9caf64017c418240a31fc37 Mon Sep 17 00:00:00 2001
From: Desmond Liu <desmond.liu@netint.ca>
Date: Mon, 5 Jan 2026 13:34:24 -0800
Subject: [PATCH] fftools/ffmpeg_demux: Fix readrate sleep calculation

Calculation of max_pts and limit_pts may overflow because adding
(int64_t + int64_t + float) results in a float that easily
overflows. This can trigger a very long av_usleep().
---
 fftools/ffmpeg_demux.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c
index cb79dd7611..193967fce1 100644
--- a/fftools/ffmpeg_demux.c
+++ b/fftools/ffmpeg_demux.c
@@ -525,7 +525,7 @@ static void readrate_sleep(Demuxer *d)
         pts = av_rescale(ds->dts, 1000000, AV_TIME_BASE);
         now = av_gettime_relative();
         wc_elapsed = now - d->wallclock_start;
-        max_pts = stream_ts_offset + initial_burst + wc_elapsed * d->readrate;
+        max_pts = stream_ts_offset + initial_burst + (int64_t)(wc_elapsed * d->readrate);
         lag = FFMAX(max_pts - pts, 0);
         if ( (!ds->lag && lag > 0.3 * AV_TIME_BASE) || ( lag > ds->lag + 0.3 * AV_TIME_BASE) ) {
             ds->lag = lag;
@@ -539,7 +539,7 @@ static void readrate_sleep(Demuxer *d)
             ds->lag = ds->resume_wc = ds->resume_pts = 0;
         if (ds->resume_wc) {
             elapsed = now - ds->resume_wc;
-            limit_pts = ds->resume_pts + elapsed * d->readrate_catchup;
+            limit_pts = ds->resume_pts + (int64_t)(elapsed * d->readrate_catchup);
         } else {
             elapsed = wc_elapsed;
             limit_pts = max_pts;
-- 
2.49.1

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