[FFmpeg-devel] [PATCH] avformat/mxfenc: fix SMPTE 436M UL for ANC

[FFmpeg-devel] [PATCH] avformat/mxfenc: fix SMPTE 436M UL for ANC

[Helmuth Schmitz via ffmpeg-devel]

The first UL of the SMPTE 436M descriptor triple in mxfenc.c used 0x0a
instead of 0x09. This caused generated MXF files without "MXF-GC Generic
ANC
Data Mapping" essence container descriptor.

This patch corrects the UL to align with SMPTE RP224, so that the ANC
descriptor is properly recognized.

Tested with MXFInspect and Adobe Premiere:
- Without the patch, the stream is not identified as ANC.
- With the patch, the ANC data is correctly detected as "Generic ANC Data".

Signed-off-by: Helmuth Schmitz <helmuthschmitz@gmail.com>

---

diff --git a/libavformat/mxfenc.c b/libavformat/mxfenc.c
index b14a480ba3..245c0853af 100644
--- a/libavformat/mxfenc.c
+++ b/libavformat/mxfenc.c
@@ -224,7 +224,7 @@ static const MXFContainerEssenceEntry
mxf_essence_container_uls[] = {
       {
0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x0a,0x04,0x01,0x02,0x02,0x01,0x00,0x00,0x00
},
       mxf_write_h264_desc },
     // S436M ANC
-    { {
0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x0a,0x0D,0x01,0x03,0x01,0x02,0x0e,0x00,0x00
},
+    { {
0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x09,0x0D,0x01,0x03,0x01,0x02,0x0E,0x00,0x00
},
       {
0x06,0x0E,0x2B,0x34,0x01,0x02,0x01,0x01,0x0D,0x01,0x03,0x01,0x17,0x01,0x02,0x00
},
       {
0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x0a,0x04,0x01,0x02,0x02,0x01,0x01,0x5C,0x00
},
       mxf_write_s436m_anc_desc },
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[FFmpeg-devel] [PATCH] avformat/mxfenc: fix SMPTE 436M UL for ANC

[Nicolas Gaullier via ffmpeg-devel]

On 9/15/25 15:26, Helmuth Schmitz via ffmpeg-devel wrote:
> The first UL of the SMPTE 436M descriptor triple in mxfenc.c used 0x0a
> instead of 0x09. This caused generated MXF files without "MXF-GC Generic
> ANC
> Data Mapping" essence container descriptor.
>
> This patch corrects the UL to align with SMPTE RP224, so that the ANC
> descriptor is properly recognized.
>
> Tested with MXFInspect and Adobe Premiere:
> - Without the patch, the stream is not identified as ANC.
> - With the patch, the ANC data is correctly detected as "Generic ANC Data".

FYI, early Omneon mxf api (>10 years back) had this bad version number, 
it was fixed later and all other implementations I have met write the 
right 0x09 value.

I don't think we care about so ancient rare broken files, so it should 
be no big deal to simply fix this.

Nicolas

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[FFmpeg-devel] Re: [PATCH] avformat/mxfenc: fix SMPTE 436M UL for ANC

[Helmuth Schmitz via ffmpeg-devel]

Hi Nicolas,

Thanks for the clarification about Omneon.
I agree that it makes sense to simply fix the UL as in this patch.

Best regards,
Helmuth

Em seg., 15 de set. de 2025 às 11:40, Nicolas Gaullier via ffmpeg-devel <
ffmpeg-devel@ffmpeg.org> escreveu:

> On 9/15/25 15:26, Helmuth Schmitz via ffmpeg-devel wrote:
> > The first UL of the SMPTE 436M descriptor triple in mxfenc.c used 0x0a
> > instead of 0x09. This caused generated MXF files without "MXF-GC Generic
> > ANC
> > Data Mapping" essence container descriptor.
> >
> > This patch corrects the UL to align with SMPTE RP224, so that the ANC
> > descriptor is properly recognized.
> >
> > Tested with MXFInspect and Adobe Premiere:
> > - Without the patch, the stream is not identified as ANC.
> > - With the patch, the ANC data is correctly detected as "Generic ANC
> Data".
>
> FYI, early Omneon mxf api (>10 years back) had this bad version number,
> it was fixed later and all other implementations I have met write the
> right 0x09 value.
>
> I don't think we care about so ancient rare broken files, so it should
> be no big deal to simply fix this.
>
> Nicolas
>
> _______________________________________________
> ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
> To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org
>
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[FFmpeg-devel] Re: [PATCH] avformat/mxfenc: fix SMPTE 436M UL for ANC

[Tomas Härdin via ffmpeg-devel]

mån 2025-09-15 klockan 10:26 -0300 skrev Helmuth Schmitz via ffmpeg-
devel:
> The first UL of the SMPTE 436M descriptor triple in mxfenc.c used
> 0x0a
> instead of 0x09. This caused generated MXF files without "MXF-GC
> Generic
> ANC
> Data Mapping" essence container descriptor.
> 
> This patch corrects the UL to align with SMPTE RP224, so that the ANC
> descriptor is properly recognized.
> 
> Tested with MXFInspect and Adobe Premiere:
> - Without the patch, the stream is not identified as ANC.
> - With the patch, the ANC data is correctly detected as "Generic ANC
> Data".

Sounds OK. We obviously shouldn't mimic broken muxers, especially when
there's a standard saying what ULs to use

/Tomas
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