[FFmpeg-devel] [PATCH] rtpdec: explicit timestamp wraparound handling

[FFmpeg-devel] [PATCH] rtpdec: explicit timestamp wraparound handling

[Clément Péron]

Change delta_timestamp to int32_t and add explicit cast to handle
RTP timestamp wraparound correctly. This fixes implementation-defined
behavior when computing negative timestamp differences due to 32-bit
wraparound.

Signed-off-by: Clément Péron <peron.clem@gmail.com>
---
 libavformat/rtpdec.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libavformat/rtpdec.c b/libavformat/rtpdec.c
index 7664ab58bd..e302203db8 100644
--- a/libavformat/rtpdec.c
+++ b/libavformat/rtpdec.c
@@ -643,6 +643,7 @@ static int rtp_set_prft(RTPDemuxContext *s, AVPacket *pkt, uint32_t timestamp) {
         return AVERROR(ENOMEM);
 
     rtcp_time = ff_parse_ntp_time(s->last_rtcp_ntp_time) - NTP_OFFSET_US;
+    /* Cast to int32_t to handle timestamp wraparound correctly */
     delta_timestamp = (int32_t)(timestamp - s->last_rtcp_timestamp);
     delta_time = av_rescale_q(delta_timestamp, s->st->time_base, AV_TIME_BASE_Q);
 
@@ -670,10 +671,11 @@ static void finalize_packet(RTPDemuxContext *s, AVPacket *pkt, uint32_t timestam
 
     if (s->last_rtcp_ntp_time != AV_NOPTS_VALUE && s->ic->nb_streams > 1) {
         int64_t addend;
-        int delta_timestamp;
+        int32_t delta_timestamp;
 
         /* compute pts from timestamp with received ntp_time */
-        delta_timestamp = timestamp - s->last_rtcp_timestamp;
+        /* Cast to int32_t to handle timestamp wraparound correctly */
+        delta_timestamp = (int32_t)(timestamp - s->last_rtcp_timestamp);
         /* convert to the PTS timebase */
         addend = av_rescale(s->last_rtcp_ntp_time - s->first_rtcp_ntp_time,
                             s->st->time_base.den,
-- 
2.48.1

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Re: [FFmpeg-devel] [PATCH] rtpdec: explicit timestamp wraparound handling

[Michael Niedermayer]

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On Sun, Jun 08, 2025 at 05:07:37PM +0200, Clément Péron wrote:
> Change delta_timestamp to int32_t and add explicit cast to handle
> RTP timestamp wraparound correctly. This fixes implementation-defined
> behavior when computing negative timestamp differences due to 32-bit
> wraparound.
> 
> Signed-off-by: Clément Péron <peron.clem@gmail.com>
> ---
>  libavformat/rtpdec.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

will apply

thx

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