________________________________________
From: James Almer
Sent: Tuesday, April 7, 2026 15:23
To: Grzegorz Rys; [email protected]
Subject: Re: [PATCH 2/3] Update jpegxs_parse_frame with GBR formats

On 4/7/2026 9:21 AM, Grzegorz Rys wrote:
> Signed-off-by: Grzegorz Rys <[email protected]>
> ---
>   libavcodec/jpegxs_parser.c | 111 +++++++++++++++++++++++++++----------
>   1 file changed, 81 insertions(+), 30 deletions(-)
>
> diff --git a/libavcodec/jpegxs_parser.c b/libavcodec/jpegxs_parser.c
> index a9750b0a02..1cc6708946 100644
> --- a/libavcodec/jpegxs_parser.c
> +++ b/libavcodec/jpegxs_parser.c
> @@ -106,6 +106,7 @@ static int jpegxs_parse_frame(AVCodecParserContext *s, 
> AVCodecContext *avctx,
>       GetBitContext gb;
>       int8_t bpc[3], log2_chroma_w[3], log2_chroma_h[3];
>       int size, marker, components;
> +    int is_rgb = 0;  // 0 = YUV, 1 = RGB
>
>       s->key_frame = 1;
>       s->pict_type = AV_PICTURE_TYPE_I;
> @@ -170,37 +171,19 @@ static int jpegxs_parse_frame(AVCodecParserContext *s, 
> AVCodecContext *avctx,
>                                  log2_chroma_w[2] != log2_chroma_w[1]))
>                       return 0;
>               }
> -
> -            switch (bpc[0]) {
> -            case 8:
> -                if (components == 1)                                     
> s->format = AV_PIX_FMT_GRAY8;
> -                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV444P;
> -                else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P;
> -                else                                                     
> s->format = AV_PIX_FMT_YUV420P;
> -                break;
> -            case 10:
> -                if (components == 1)                                     
> s->format = AV_PIX_FMT_GRAY10;
> -                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV444P10;
> -                else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P10;
> -                else                                                     
> s->format = AV_PIX_FMT_YUV420P10;
> -                break;
> -            case 12:
> -                if (components == 1)                                     
> s->format = AV_PIX_FMT_GRAY12;
> -                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV444P12;
> -                else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P12;
> -                else                                                     
> s->format = AV_PIX_FMT_YUV420P12;
> -                break;
> -            case 14:
> -                if (components == 1)                                     
> s->format = AV_PIX_FMT_GRAY14;
> -                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV444P14;
> -                else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P14;
> -                else                                                     
> s->format = AV_PIX_FMT_YUV420P14;
> -                break;
> -            default:
> -                s->format = AV_PIX_FMT_NONE;
> -                break;
> +            bytestream2_skip(&gbc, FFMAX(size - 2, 0));
> +            break;
> +        case JPEGXS_MARKER_CTS:
> +            size = bytestream2_get_be16(&gbc);
> +            if (size >= 3) {
> +                int colour_spec = bytestream2_get_byte(&gbc);
> +                // colour_spec: 0=YCbCr, 1=RGB, 2=Gray, ...
> +                if (colour_spec == 1)
> +                    is_rgb = 1;
>               }
> -            return 0;
> +            bytestream2_skip(&gbc, FFMAX(size - 3, 0));
> +            // Format decision after CTS
> +            goto format_decision;
>           default:
>               size = bytestream2_get_be16(&gbc);
>               bytestream2_skip(&gbc, FFMAX(size - 2, 0));
> @@ -208,6 +191,74 @@ static int jpegxs_parse_frame(AVCodecParserContext *s, 
> AVCodecContext *avctx,
>           }
>       }
>
> +format_decision:
> +    // Determine pixel format based on bit depth and chroma subsampling
> +    switch (bpc[0]) {

Nothing ensures a CDT was seen before a CTS one, or that either of them
were seen at all. If that happens, bpc[0] here will be uninitialized.

Keep the code below inside the while() loop, and add a check for CDT
presence before going through with CDT parsing.

> +    case 8:
> +        if (components == 1) {
> +            s->format = AV_PIX_FMT_GRAY8;
> +        } else if (is_rgb) {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
> +                s->format = AV_PIX_FMT_GBRP;
> +            } else {
> +                s->format = AV_PIX_FMT_NONE;  // Invalid RGB with chroma 
> subsampling
> +            }
> +        } else {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format = 
> AV_PIX_FMT_YUV444P;
> +            else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P;
> +            else                                                     
> s->format = AV_PIX_FMT_YUV420P;
> +        }
> +        break;
> +    case 10:
> +        if (components == 1) {
> +            s->format = AV_PIX_FMT_GRAY10;
> +        } else if (is_rgb) {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
> +                s->format = AV_PIX_FMT_GBRP10LE;
> +            } else {
> +                s->format = AV_PIX_FMT_NONE;
> +            }
> +        } else {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format = 
> AV_PIX_FMT_YUV444P10;
> +            else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P10;
> +            else                                                     
> s->format = AV_PIX_FMT_YUV420P10;
> +        }
> +        break;
> +    case 12:
> +        if (components == 1) {
> +            s->format = AV_PIX_FMT_GRAY12;
> +        } else if (is_rgb) {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
> +                s->format = AV_PIX_FMT_GBRP12LE;
> +            } else {
> +                s->format = AV_PIX_FMT_NONE;
> +            }
> +        } else {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format = 
> AV_PIX_FMT_YUV444P12;
> +            else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P12;
> +            else                                                     
> s->format = AV_PIX_FMT_YUV420P12;
> +        }
> +        break;
> +    case 14:
> +        if (components == 1) {
> +            s->format = AV_PIX_FMT_GRAY14;
> +        } else if (is_rgb) {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
> +                s->format = AV_PIX_FMT_GBRP14LE;
> +            } else {
> +                s->format = AV_PIX_FMT_NONE;
> +            }
> +        } else {
> +            if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format = 
> AV_PIX_FMT_YUV444P14;
> +            else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
> s->format = AV_PIX_FMT_YUV422P14;
> +            else                                                     
> s->format = AV_PIX_FMT_YUV420P14;
> +        }
> +        break;
> +    default:
> +        s->format = AV_PIX_FMT_NONE;
> +        break;
> +    }
> +
>       return 0;
>   }
>

Updated patch:

>From a0518227f4ccdc004f7cd332cf00dd1101b38fbf Mon Sep 17 00:00:00 2001
From: Grzegorz Rys <[email protected]>
Date: Thu, 2 Apr 2026 11:03:44 +0200
Subject: [PATCH 2/3] Update jpegxs_parse_frame with GBR formats

Signed-off-by: Grzegorz Rys <[email protected]>
---
 libavcodec/jpegxs_parser.c | 102 +++++++++++++++++++++++++++++++-------------
 1 file changed, 60 insertions(+), 42 deletions(-)

--- a/libavcodec/jpegxs_parser.c
+++ b/libavcodec/jpegxs_parser.c
@@ -106,6 +106,7 @@
     GetBitContext gb;
     int8_t bpc[3], log2_chroma_w[3], log2_chroma_h[3];
     int size, marker, components;
+    int has_cdt = 0, has_cts = 0, is_rgb = 0;
 
     s->key_frame = 1;
     s->pict_type = AV_PICTURE_TYPE_I;
@@ -170,42 +171,101 @@
                                log2_chroma_w[2] != log2_chroma_w[1]))
                     return 0;
             }
+            has_cdt = 1;
+            bytestream2_skip(&gbc, FFMAX(size - 2, 0));
+            break;
+        case JPEGXS_MARKER_CTS:
+            size = bytestream2_get_be16(&gbc);
+            if (size >= 3) {
+                int colour_spec = bytestream2_get_byte(&gbc);
+
+                has_cts = 1;
+                is_rgb = colour_spec == 1;
+            }
+            bytestream2_skip(&gbc, FFMAX(size - 3, 0));
+            break;
+        default:
+            size = bytestream2_get_be16(&gbc);
+            bytestream2_skip(&gbc, FFMAX(size - 2, 0));
+            break;
+        }
+
+        if (!has_cdt)
+            continue;
 
-            switch (bpc[0]) {
-            case 8:
-                if (components == 1)                                     
s->format = AV_PIX_FMT_GRAY8;
-                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV444P;
+        if (components == 3 &&
+            log2_chroma_w[1] == 1 &&
+            log2_chroma_h[1] == 1 &&
+            !has_cts)
+            continue;
+
+        switch (bpc[0]) {
+        case 8:
+            if (components == 1) {
+                s->format = AV_PIX_FMT_GRAY8;
+            } else if (is_rgb) {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
+                    s->format = AV_PIX_FMT_GBRP;
+                } else {
+                    s->format = AV_PIX_FMT_NONE;
+                }
+            } else {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format 
= AV_PIX_FMT_YUV444P;
                 else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV422P;
                 else                                                     
s->format = AV_PIX_FMT_YUV420P;
-                break;
-            case 10:
-                if (components == 1)                                     
s->format = AV_PIX_FMT_GRAY10;
-                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV444P10;
+            }
+            break;
+        case 10:
+            if (components == 1) {
+                s->format = AV_PIX_FMT_GRAY10;
+            } else if (is_rgb) {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
+                    s->format = AV_PIX_FMT_GBRP10LE;
+                } else {
+                    s->format = AV_PIX_FMT_NONE;
+                }
+            } else {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format 
= AV_PIX_FMT_YUV444P10;
                 else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV422P10;
                 else                                                     
s->format = AV_PIX_FMT_YUV420P10;
-                break;
-            case 12:
-                if (components == 1)                                     
s->format = AV_PIX_FMT_GRAY12;
-                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV444P12;
+            }
+            break;
+        case 12:
+            if (components == 1) {
+                s->format = AV_PIX_FMT_GRAY12;
+            } else if (is_rgb) {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
+                    s->format = AV_PIX_FMT_GBRP12LE;
+                } else {
+                    s->format = AV_PIX_FMT_NONE;
+                }
+            } else {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format 
= AV_PIX_FMT_YUV444P12;
                 else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV422P12;
                 else                                                     
s->format = AV_PIX_FMT_YUV420P12;
-                break;
-            case 14:
-                if (components == 1)                                     
s->format = AV_PIX_FMT_GRAY14;
-                else if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV444P14;
+            }
+            break;
+        case 14:
+            if (components == 1) {
+                s->format = AV_PIX_FMT_GRAY14;
+            } else if (is_rgb) {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) {
+                    s->format = AV_PIX_FMT_GBRP14LE;
+                } else {
+                    s->format = AV_PIX_FMT_NONE;
+                }
+            } else {
+                if (log2_chroma_w[1] == 1 && log2_chroma_h[1] == 1) s->format 
= AV_PIX_FMT_YUV444P14;
                 else if (log2_chroma_w[1] == 2 && log2_chroma_h[1] == 1) 
s->format = AV_PIX_FMT_YUV422P14;
                 else                                                     
s->format = AV_PIX_FMT_YUV420P14;
-                break;
-            default:
-                s->format = AV_PIX_FMT_NONE;
-                break;
             }
-            return 0;
+            break;
         default:
-            size = bytestream2_get_be16(&gbc);
-            bytestream2_skip(&gbc, FFMAX(size - 2, 0));
+            s->format = AV_PIX_FMT_NONE;
             break;
         }
+
+        return 0;
     }
 
     return 0;

-- 
2.51.0


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