[FFmpeg-devel] [PATCH 01/10] crystalhd: Fix up the missing first sample

[Philip Langdale]

Why on earth the hardware returns garbage for the first sample of
a decoded picture is anyone's guess. The simplest reasonable way
to patch it up is to copy the first sample of the second line. This
should result in the correct chroma values (because the data was
original 4:2:0 upsampled to 4:2:2) even if the luma is isn't.

Signed-off-by: Philip Langdale <philipl at overt.org>
---
 libavcodec/crystalhd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/libavcodec/crystalhd.c b/libavcodec/crystalhd.c
index 9120940..137ed20 100644
--- a/libavcodec/crystalhd.c
+++ b/libavcodec/crystalhd.c
@@ -706,6 +706,15 @@ static inline CopyRet copy_frame(AVCodecContext *avctx,
 
     av_log(priv->avctx, AV_LOG_VERBOSE, "CrystalHD: Copying out frame\n");
 
+    /*
+     * The hardware doesn't return the first sample of a picture.
+     * Ignoring why it behaves this way, it's better to copy the sample from
+     * the second line, rather than the next sample across because the chroma
+     * values should be correct (assuming the decoded video was 4:2:0, which
+     * it was).
+     */
+    *((uint32_t *)src) = *((uint32_t *)(src + sStride));
+
     if (interlaced) {
         int dY = 0;
         int sY = 0;
-- 
2.9.3