[FFmpeg-devel] [PATCHv2] avcodec/leaddec: support format 0x1006

* [FFmpeg-devel] [PATCHv2] avcodec/leaddec: support format 0x1006
@ 2025-01-19  9:49 Peter Ross
  2025-02-05 22:21 ` Peter Ross
  0 siblings, 1 reply; 2+ messages in thread
From: Peter Ross @ 2025-01-19  9:49 UTC (permalink / raw)
  To: ffmpeg-devel


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Fixes ticket #10658.
---

Tested with some different vertical resolution alignments.

When the vertical resolution is not aligned to macroblock height, the
reference encoder & decoder performs buggy placement of the initial
field. Its an internal bug, but because the encoder and decoder are
aligned, end-user does not see it.

FFmpeg decoder does not reproduce this behaviour.

 libavcodec/leaddec.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/libavcodec/leaddec.c b/libavcodec/leaddec.c
index 88387902ca..e6a91faabc 100644
--- a/libavcodec/leaddec.c
+++ b/libavcodec/leaddec.c
@@ -164,6 +164,10 @@ static int lead_decode_frame(AVCodecContext *avctx, AVFrame * frame,
     case 0x1000:
         avctx->pix_fmt = AV_PIX_FMT_YUV420P;
         break;
+    case 0x1006:
+        fields = 2;
+        avctx->pix_fmt = AV_PIX_FMT_YUV420P;
+        break;
     case 0x2000:
         avctx->pix_fmt = AV_PIX_FMT_YUV444P;
         break;
@@ -237,7 +241,8 @@ static int lead_decode_frame(AVCodecContext *avctx, AVFrame * frame,
                         return ret;
                 }
     } else if (avctx->pix_fmt == AV_PIX_FMT_YUV420P) {
-        for (int mb_y = 0; mb_y < (avctx->height + 15) / 16; mb_y++)
+        for (int f = 0; f < fields; f++)
+        for (int mb_y = 0; mb_y < (avctx->height + 15) / 16 / fields; mb_y++)
             for (int mb_x = 0; mb_x < (avctx->width + 15) / 16; mb_x++)
                 for (int b = 0; b < (yuv20p_half ? 4 : 6); b++) {
                     int luma_block = yuv20p_half ? 2 : 4;
@@ -258,8 +263,8 @@ static int lead_decode_frame(AVCodecContext *avctx, AVFrame * frame,
 
                     ret = decode_block(s, &gb, dc_vlc, dc_bits, ac_vlc, ac_bits,
                         dc_pred + plane, dequant[!(b < 4)],
-                        frame->data[plane] + y*frame->linesize[plane] + x,
-                        (yuv20p_half && b < 2 ? 2 : 1) * frame->linesize[plane]);
+                        frame->data[plane] + (f + y*fields)*frame->linesize[plane] + x,
+                        (yuv20p_half && b < 2 ? 2 : 1) * fields * frame->linesize[plane]);
                     if (ret < 0)
                         return ret;
 
-- 
2.45.2

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)

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