[FFmpeg-devel] [PATCH] avformat/rtpenc: Add flag AVFMT_NODIMENSIONS.

[FFmpeg-devel] [PATCH] avformat/rtpenc: Add flag AVFMT_NODIMENSIONS.

[koushd]

From: Koushik Dutta <koushd@gmail.com>

Not all rtp formats require the video dimensions to be available
up front. H264 and HEVC will send them as stream parameters.
The flag is restrictive and prevents RTP repacketization
without parsing the codec information out of the stream.

This change checks to see if the codec parameters are available
on the rtp formats that need it.

Signed-off-by: Koushik Dutta <koushd@gmail.com>
---
 libavformat/rtpenc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libavformat/rtpenc.c b/libavformat/rtpenc.c
index 7b4ae37d13..0ea1cb2be4 100644
--- a/libavformat/rtpenc.c
+++ b/libavformat/rtpenc.c
@@ -621,10 +621,18 @@ static int rtp_write_packet(AVFormatContext *s1, AVPacket *pkt)
         rtp_send_ilbc(s1, pkt->data, size);
         break;
     case AV_CODEC_ID_MJPEG:
+        if (st->codecpar->width <= 0 || st->codecpar->height <= 0) {
+            av_log(s1, AV_LOG_ERROR, "dimensions not set\n");
+            return AVERROR(EINVAL);
+        }
         ff_rtp_send_jpeg(s1, pkt->data, size);
         break;
     case AV_CODEC_ID_BITPACKED:
     case AV_CODEC_ID_RAWVIDEO: {
+        if (st->codecpar->width <= 0 || st->codecpar->height <= 0) {
+            av_log(s1, AV_LOG_ERROR, "dimensions not set\n");
+            return AVERROR(EINVAL);
+        }
         int interlaced = st->codecpar->field_order != AV_FIELD_PROGRESSIVE;
 
         ff_rtp_send_raw_rfc4175(s1, pkt->data, size, interlaced, 0);
@@ -671,5 +679,5 @@ const FFOutputFormat ff_rtp_muxer = {
     .write_packet      = rtp_write_packet,
     .write_trailer     = rtp_write_trailer,
     .p.priv_class      = &rtp_muxer_class,
-    .p.flags           = AVFMT_TS_NONSTRICT,
+    .p.flags           = AVFMT_NODIMENSIONS | AVFMT_TS_NONSTRICT,
 };
-- 
2.39.5 (Apple Git-154)

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Re: [FFmpeg-devel] [PATCH] avformat/rtpenc: Add flag AVFMT_NODIMENSIONS.

[Michael Niedermayer]

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Hi

On Wed, Mar 26, 2025 at 01:13:13PM -0700, koushd@gmail.com wrote:
> From: Koushik Dutta <koushd@gmail.com>
> 
> Not all rtp formats require the video dimensions to be available
> up front. H264 and HEVC will send them as stream parameters.
> The flag is restrictive and prevents RTP repacketization
> without parsing the codec information out of the stream.
> 
> This change checks to see if the codec parameters are available
> on the rtp formats that need it.
> 
> Signed-off-by: Koushik Dutta <koushd@gmail.com>
> ---
>  libavformat/rtpenc.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)

In general when muxing a stream, the dimensions are known

Can you explain what you are doing with rtpenc that lacks
known dimensions ?
is this some sort of low latency remuxing ?

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Some people wanted to paint the bikeshed green, some blue and some pink.
People argued and fought, when they finally agreed, only rust was left.

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Re: [FFmpeg-devel] [PATCH] avformat/rtpenc: Add flag AVFMT_NODIMENSIONS.

[Koushik Dutta]

Yes, that’s what I am doing. I am repacketizing h264 and hevc without
inspection of the stream itself. RTSP over tcp can transmit rtp packets up
to 64k. Some cameras utilize this to reduce fragmentation overhead but
those large packets need to be fragmented for udp rebroadcast on typical
network mtu.

I could inspect the stream for sps and then parse the dimensions out of
there, or maybe set some dummy values on the rtp encoder somehow and work
around this. But neither of those seemed like proper solutions given rtp
doesn’t need to know the steam dimensions for all but 2 codecs.

On Fri, Mar 28, 2025 at 4:39 PM Michael Niedermayer <michael@niedermayer.cc>
wrote:

> Hi
>
> On Wed, Mar 26, 2025 at 01:13:13PM -0700, koushd@gmail.com wrote:
> > From: Koushik Dutta <koushd@gmail.com>
> >
> > Not all rtp formats require the video dimensions to be available
> > up front. H264 and HEVC will send them as stream parameters.
> > The flag is restrictive and prevents RTP repacketization
> > without parsing the codec information out of the stream.
> >
> > This change checks to see if the codec parameters are available
> > on the rtp formats that need it.
> >
> > Signed-off-by: Koushik Dutta <koushd@gmail.com>
> > ---
> >  libavformat/rtpenc.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
>
> In general when muxing a stream, the dimensions are known
>
> Can you explain what you are doing with rtpenc that lacks
> known dimensions ?
> is this some sort of low latency remuxing ?
>
> thx
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Some people wanted to paint the bikeshed green, some blue and some pink.
> People argued and fought, when they finally agreed, only rust was left.
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
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Re: [FFmpeg-devel] [PATCH] avformat/rtpenc: Add flag AVFMT_NODIMENSIONS.

[Michael Niedermayer]

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Hi Koushik

On Fri, Mar 28, 2025 at 11:30:05PM -0700, Koushik Dutta wrote:
> Yes, that’s what I am doing. I am repacketizing h264 and hevc without
> inspection of the stream itself. RTSP over tcp can transmit rtp packets up
> to 64k. Some cameras utilize this to reduce fragmentation overhead but
> those large packets need to be fragmented for udp rebroadcast on typical
> network mtu.
> 
> I could inspect the stream for sps and then parse the dimensions out of
> there, or maybe set some dummy values on the rtp encoder somehow and work
> around this. But neither of those seemed like proper solutions given rtp
> doesn’t need to know the steam dimensions for all but 2 codecs.

ok, will apply

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope

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