[FFmpeg-devel] [PATCH] avcodec/cuvidddec: Guess pixel format based on probed bit depth

[Roman Arzumanyan <r.arzumanyan@visionlabs.ai>]

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Hello world,

This patch adds a pixel format guess based on probed bit depth.
With current FFMpeg ToT, when the cuvid codec is opened, input sw_pix_fmt
is AV_PIX_FMT_NV12 until the first frame is decoded. Even if input has 10
or 12 bit depth, the format will be NV12 for some time.

What's the need for this patch ?
Applications that rely on libavcodec will have a chance to calculate the
proper amount of vRAM required to store a reconstructed video frame before
decoding begins.

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From ae80b12d10a4de4aa96a4670b72accbfc5a87631 Mon Sep 17 00:00:00 2001
From: Roman Arzumanyan <r.arzumanyan@visionlabs.ai>
Date: Thu, 1 Aug 2024 16:35:22 +0300
Subject: [PATCH] Guess pixel format based on bit depth

---
 libavcodec/cuviddec.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/libavcodec/cuviddec.c b/libavcodec/cuviddec.c
index f88ad75e88..2205b1536a 100644
--- a/libavcodec/cuviddec.c
+++ b/libavcodec/cuviddec.c
@@ -834,7 +834,7 @@ static av_cold int cuvid_decode_init(AVCodecContext *avctx)
     int ret = 0;
 
     enum AVPixelFormat pix_fmts[3] = { AV_PIX_FMT_CUDA,
-                                       AV_PIX_FMT_NV12,
+                                       AV_PIX_FMT_NONE,
                                        AV_PIX_FMT_NONE };
 
     int probed_width = avctx->coded_width ? avctx->coded_width : 1280;
@@ -845,11 +845,26 @@ static av_cold int cuvid_decode_init(AVCodecContext *avctx)
     if (probe_desc && probe_desc->nb_components)
         probed_bit_depth = probe_desc->comp[0].depth;
 
+    // Arbitrarily pick pixel format based on bit depth.
+    switch (probed_bit_depth) {
+    case 8:
+        pix_fmts[1] = AV_PIX_FMT_NV12;
+        break;        
+    case 10:
+        pix_fmts[1] = AV_PIX_FMT_P010;
+        break;
+    case 12:
+        pix_fmts[1] = AV_PIX_FMT_P012;
+        break;
+    default:
+        break;
+    }
+
     ctx->pkt = avctx->internal->in_pkt;
     // Accelerated transcoding scenarios with 'ffmpeg' require that the
     // pix_fmt be set to AV_PIX_FMT_CUDA early. The sw_pix_fmt, and the
     // pix_fmt for non-accelerated transcoding, do not need to be correct
-    // but need to be set to something. We arbitrarily pick NV12.
+    // but need to be set to something.
     ret = ff_get_format(avctx, pix_fmts);
     if (ret < 0) {
         av_log(avctx, AV_LOG_ERROR, "ff_get_format failed: %d\n", ret);
-- 
2.34.1


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