[FFmpeg-devel] [PATCH] avformat/rtpenc: use unsigned type for ssrc option

[FFmpeg-devel] [PATCH] avformat/rtpenc: use unsigned type for ssrc option

[NEKO ASAKURA via ffmpeg-devel]

The ssrc option used AV_OPT_TYPE_INT with range [INT_MIN, INT_MAX],
but the underlying struct field is uint32_t and RFC 3550 defines SSRC
as a 32-bit identifier covering the full [0, UINT32_MAX] range. This
caused ffmpeg to reject any SSRC value above INT_MAX (~2.1 billion),
which is roughly half of all valid values.

The auto-generated fallback path (av_get_random_seed()) already
returns uint32_t and can produce values above INT_MAX, creating an
inconsistency where the automatic path succeeds but the explicit
-ssrc option rejects the same value.

Change the option to AV_OPT_TYPE_UINT with range [0, UINT32_MAX]
to match the field type and allow the full identifier space.

Fixes ticket #9080.

Signed-off-by: Neko Asakura <neko.asakura@outlook.com>
---
 libavformat/rtpenc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/rtpenc.c b/libavformat/rtpenc.c
index 3602b081..6d8e95f4 100644
--- a/libavformat/rtpenc.c
+++ b/libavformat/rtpenc.c
@@ -33,7 +33,7 @@
 static const AVOption options[] = {
     FF_RTP_FLAG_OPTS(RTPMuxContext, flags),
     { "payload_type", "Specify RTP payload type", offsetof(RTPMuxContext, payload_type), AV_OPT_TYPE_INT, {.i64 = -1 }, -1, 127, AV_OPT_FLAG_ENCODING_PARAM },
-    { "ssrc", "Stream identifier", offsetof(RTPMuxContext, ssrc), AV_OPT_TYPE_INT, { .i64 = 0 }, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { "ssrc", "Stream identifier", offsetof(RTPMuxContext, ssrc), AV_OPT_TYPE_UINT, { .i64 = 0 }, 0, UINT32_MAX, AV_OPT_FLAG_ENCODING_PARAM },
     { "cname", "CNAME to include in RTCP SR packets", offsetof(RTPMuxContext, cname), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, AV_OPT_FLAG_ENCODING_PARAM },
     { "seq", "Starting sequence number", offsetof(RTPMuxContext, seq), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, AV_OPT_FLAG_ENCODING_PARAM },
     { NULL },
-- 
2.43.0
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[FFmpeg-devel] Re: [PATCH] avformat/rtpenc: use unsigned type for ssrc option

[Michael Niedermayer via ffmpeg-devel]

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On Fri, Feb 20, 2026 at 08:24:08PM +0000, NEKO ASAKURA via ffmpeg-devel wrote:
> The ssrc option used AV_OPT_TYPE_INT with range [INT_MIN, INT_MAX],
> but the underlying struct field is uint32_t and RFC 3550 defines SSRC
> as a 32-bit identifier covering the full [0, UINT32_MAX] range. This
> caused ffmpeg to reject any SSRC value above INT_MAX (~2.1 billion),
> which is roughly half of all valid values.
> 
> The auto-generated fallback path (av_get_random_seed()) already
> returns uint32_t and can produce values above INT_MAX, creating an
> inconsistency where the automatic path succeeds but the explicit
> -ssrc option rejects the same value.
> 
> Change the option to AV_OPT_TYPE_UINT with range [0, UINT32_MAX]
> to match the field type and allow the full identifier space.
> 
> Fixes ticket #9080.
> 
> Signed-off-by: Neko Asakura <neko.asakura@outlook.com>
> ---
>  libavformat/rtpenc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

will be applied as soon as someone approves: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22302/commits

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 

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[FFmpeg-devel] Re: [PATCH] avformat/rtpenc: use unsigned type for ssrc option

[Jack Lau via ffmpeg-devel]

> On Feb 27, 2026, at 08:15, Michael Niedermayer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org> wrote:
> 
> On Fri, Feb 20, 2026 at 08:24:08PM +0000, NEKO ASAKURA via ffmpeg-devel wrote:
>> The ssrc option used AV_OPT_TYPE_INT with range [INT_MIN, INT_MAX],
>> but the underlying struct field is uint32_t and RFC 3550 defines SSRC
>> as a 32-bit identifier covering the full [0, UINT32_MAX] range. This
>> caused ffmpeg to reject any SSRC value above INT_MAX (~2.1 billion),
>> which is roughly half of all valid values.
>> 
>> The auto-generated fallback path (av_get_random_seed()) already
>> returns uint32_t and can produce values above INT_MAX, creating an
>> inconsistency where the automatic path succeeds but the explicit
>> -ssrc option rejects the same value.
>> 
>> Change the option to AV_OPT_TYPE_UINT with range [0, UINT32_MAX]
>> to match the field type and allow the full identifier space.
>> 
>> Fixes ticket #9080.
>> 
>> Signed-off-by: Neko Asakura <neko.asakura@outlook.com>
>> ---
>> libavformat/rtpenc.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> will be applied as soon as someone approves: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22302/commits

If no one else approves it after a day, I can give it my approval. I ensure this fixes an issue.

In WHIP, I previously added a workaround where I converted the 32 bit SSRC to an int and passed it as a string to match the SSRC option in rtpenc. 

```
snprintf(buf, sizeof(buf), "%d", is_video? whip->video_ssrc : whip->audio_ssrc);
av_dict_set(&opts, "ssrc", buf, 0);
```

And it finally was converterd back to uint32_t because ssrc is declared as uint32_t in RTPMuxContext

After applying this rtpenc patch, I will directly correctly pass SSRC as a uint32_t in whip.c:

> 
> [...]
> 
> -- 
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> 
> The educated differ from the uneducated as much as the living from the
> dead. -- Aristotle 
> _______________________________________________
> ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
> To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org

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