Fix Encoder Quality Options Not Being Applied

.gitignore

@@ -47,4 +47,5 @@ desktop.ini
 /O5Theme.md
 
 # Developer Utility Files
-/REVIEW_CHECKLIST.md
+/REVIEW_CHECKLIST.md
+/REVIEW_FFMPEG.md

Util/FFmpeg/FFmpegNativeEncoder.cs

@@ -83,7 +83,7 @@ namespace ADOFAIRenderer.Util.FFmpeg
             /// <summary>Frames per second (e.g., 60.0, 29.97, etc.).</summary>
             public double FPS;
 
-            /// <summary>Video codec type to use (H264, H265, AV1, VP9).</summary>
+            /// <summary>Video codec type to use (H264, H265, AV1, VP9, VVC).</summary>
             public Codec Codec;
 
             /// <summary>Bitrate control mode (CQP, CBR, VBR).</summary>
@@ -825,7 +825,7 @@ namespace ADOFAIRenderer.Util.FFmpeg
         /// Reference - CQP options per encoder:
         ///   NVENC:     "qp" (single value applied to I/P/B frames)
         ///   AMF:       "qp_i" + "qp_p" (I-frame and P-frame configured separately)
-        ///   QSV:       "global_quality" (Intel unique option)
+        ///   QSV:       AVCodecContext.global_quality (Intel ICQ mode)
         ///   Software:  "crf" (Constant Rate Factor, smarter quality control)
         ///
         /// Reference: https://ffmpeg.org/doxygen/trunk/structAVCodecContext.html
@@ -847,11 +847,21 @@ namespace ADOFAIRenderer.Util.FFmpeg
                         _pCodecContext->rc_max_rate = _pCodecContext->rc_min_rate = _settings.TargetBitrate * 1000L;
                         _pCodecContext->rc_buffer_size = _settings.TargetBitrate * 1000;
 
-                        // nal-hrd=cbr: x264/x265 dedicated option. Generates CBR bitstream matching
+                        // HRD (Hypothetical Reference Decoder) signaling for CBR output, used for streaming compatibility.
-                        // NAL HRD (Hypothetical Reference Decoder) specification. May be required for streaming compatibility.
+                        //   libx264: "nal-hrd=cbr" writes the NAL HRD information and pads filler data to keep the bitrate constant.
-                        if (encoder == VideoEncoder.Libx264 || encoder == VideoEncoder.Libx265)
+                        //            FFmpeg's option description: "Signal HRD information (requires vbv-bufsize; cbr not allowed in .mp4)".
+                        //            Reference: https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/libx264.c ("nal-hrd": none/vbr/cbr)
+                        //   libx265: "x265-params" = "hrd=1" (--hrd: "Enable the signaling of HRD parameters to the decoder")
+                        //            + "strict-cbr=1" (--strict-cbr: "Enables stricter conditions to control bitrate deviance
+                        //            from the target bitrate in ABR mode").
+                        //            Reference: https://x265.readthedocs.io/en/master/cli.html
+                        if (encoder == VideoEncoder.Libx264)
                         {
-                            ffmpeg.av_opt_set(_pCodecContext->priv_data, "nal-hrd", "cbr", 0);
+                            TrySetOption("nal-hrd", "cbr");
+                        }
+                        else if (encoder == VideoEncoder.Libx265)
+                        {
+                            TrySetOption("x265-params", "hrd=1:strict-cbr=1");
                         }
                     }
                     break;
@@ -875,38 +885,77 @@ namespace ADOFAIRenderer.Util.FFmpeg
                     break;
 
                 case RateControlMode.CQP:
+                    // Valid quality range per encoder. The range of the private options is read from the
+                    // encoder's option definition (AVOption min/max); a declared minimum of -1 means "auto".
+                    //   NVENC:    "qp"    H.264/HEVC 0~51, AV1 0~255
+                    //             (libavcodec/nvenc_h264.c, nvenc_hevc.c: "qp" -1~51 / libavcodec/nvenc_av1.c: "qp" -1~255)
+                    //   AMF:      "qp_i"  H.264/HEVC 0~51, AV1 0~255
+                    //             (libavcodec/amfenc_h264.c, amfenc_hevc.c: "qp_i" -1~51 / libavcodec/amfenc_av1.c: "qp_i" -1~255)
+                    //   QSV:      AVCodecContext.global_quality 1~51
+                    //   VVC:      "qp"    0~63 (libavcodec/libvvenc.c: "qp" -1~63)
+                    //   Software: "crf"   x264/x265 0~51 (https://x265.readthedocs.io/en/master/cli.html: --crf 0..51.0),
+                    //             VP9/AV1 0~63 (libavcodec/libvpxenc.c, libaomenc.c: "crf" -1~63 / libavcodec/libsvtav1.c: "crf" 0~63)
+                    // Reference: https://github.com/FFmpeg/FFmpeg/tree/master/libavcodec
+                    int qpMin, qpMax;
+                    if (encoder.Kind == EncoderKind.QSV)
+                    {
+                        // QSV runs in ICQ (Intelligent Constant Quality) mode when global_quality > 0 and rc_max_rate is 0;
+                        // global_quality 0 selects the encoder's default CQP. The ICQ quality is clamped to 1~51 by FFmpeg:
+                        //   libavcodec/qsvenc.c: q->param.mfx.ICQQuality = av_clip(avctx->global_quality, 1, 51);
+                        // Reference: https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/qsvenc.c
+                        qpMin = 1;
+                        qpMax = 51;
+                    }
+                    else if (encoder.Kind == EncoderKind.NVENC) (qpMin, qpMax) = GetQualityRange("qp");
+                    else if (encoder.Kind == EncoderKind.AMF) (qpMin, qpMax) = GetQualityRange("qp_i");
+                    else if (encoder == VideoEncoder.LibVvenc) (qpMin, qpMax) = GetQualityRange("qp");
+                    else (qpMin, qpMax) = GetQualityRange("crf"); // Software encoder (libx264, libx265, libvpx-vp9, etc.)
+
                     // Default value 18: Quality close to "visually lossless" in H.264.
                     // Provides similar level of quality in other codecs as well.
-                    var qpValue = _settings.QualityValue is >= 0 and <= 51 ? _settings.QualityValue : 18;
+                    const int defaultQuality = 18;
+                    var requestedQp = _settings.QualityValue;
+                    int qpValue;
+                    if (requestedQp < 0)
+                    {
+                        qpValue = Math.Clamp(defaultQuality, qpMin, qpMax);
+                        Melon<RenderMod>.Logger.Warning($"{encoder.Name}: Invalid quality value {requestedQp}. Using {qpValue}.");
+                    }
+                    else
+                    {
+                        qpValue = Math.Clamp(requestedQp, qpMin, qpMax);
+                        if (qpValue != requestedQp)
+                            Melon<RenderMod>.Logger.Warning($"{encoder.Name}: Quality value {requestedQp} is outside the supported range {qpMin}~{qpMax}. Using {qpValue}.");
+                    }
 
                     if (encoder.Kind == EncoderKind.NVENC)
                     {
                         // NVENC: Applies same QP to I/P/B frames with single "qp" option
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "qp", qpValue.ToString(), 0);
+                        TrySetOption("qp", qpValue.ToString());
                     }
                     else if (encoder.Kind == EncoderKind.AMF)
                     {
                         // AMF: QP for I-frame (qp_i) and P-frame (qp_p) must be set separately.
                         // Since B-frames are disabled, qp_b is not set.
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "qp_i", qpValue.ToString(), 0);
+                        TrySetOption("qp_i", qpValue.ToString());
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "qp_p", qpValue.ToString(), 0);
+                        TrySetOption("qp_p", qpValue.ToString());
                     }
                     else if (encoder.Kind == EncoderKind.QSV)
                     {
-                        // QSV: Uses ICQ (Intelligent Constant Quality) mode with "global_quality" option
+                        // QSV: ICQ (Intelligent Constant Quality) mode, configured with AVCodecContext.global_quality.
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "global_quality", qpValue.ToString(), 0);
+                        _pCodecContext->global_quality = qpValue;
                     }
                     else if (encoder == VideoEncoder.LibVvenc)
                     {
                         // libvvenc: Specifies Constant QP mode with "qp" option
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "qp", qpValue.ToString(), 0);
+                        TrySetOption("qp", qpValue.ToString());
                     }
-                    else // Software encoder (libx264, libx265, libvpx-vp9, etc.)
+                    else
                     {
                         // CRF (Constant Rate Factor): Smarter quality control than QP.
                         // Automatically adjusts bitrate according to scene complexity to maintain consistent visual quality.
-                        // Range: 0 (lossless) ~ 51 (lowest quality). Typically between 18 and 28.
+                        // Range: 0 (lossless) ~ 51 (lowest quality) for x264/x265, 0~63 for VP9/AV1. Typically between 18 and 28.
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "crf", qpValue.ToString(), 0);
+                        TrySetOption("crf", qpValue.ToString());
                     }
                     break;
                 default:
@@ -914,6 +963,49 @@ namespace ADOFAIRenderer.Util.FFmpeg
             }
         }
 
+        /// <summary>
+        /// Sets a private option (priv_data) of the encoder.
+        /// Returns true when FFmpeg accepts the option. Otherwise logs a warning with the FFmpeg error and returns false.
+        /// </summary>
+        private bool TrySetOption(string name, string value)
+        {
+            var ret = ffmpeg.av_opt_set(_pCodecContext->priv_data, name, value, 0);
+            if (ret >= 0) return true;
+
+            Melon<RenderMod>.Logger.Warning($"[Encoder] Option '{name}={value}' was not applied: {GetFFmpegErrorString(ret)} (Code: {ret})");
+            return false;
+        }
+
+        /// <summary>
+        /// Largest declared maximum that is treated as an actual quality range.
+        /// A declared maximum above this value is treated as unbounded, and the fallback range 0~51 is used.
+        /// The largest bounded quality range among the supported encoders is 0~255 (AV1 NVENC/AMF), while
+        /// libx264/libx265 declare "crf" as -1~FLT_MAX (libavcodec/libx264.c, libx265.c).
+        /// </summary>
+        private const double MaxMeaningfulQualityLimit = 1000;
+
+        /// <summary>
+        /// Returns the valid range of a private quality option of the encoder from its option definition (AVOption min/max).
+        /// e.g. 0~51 for H.264/HEVC, 0~63 for VP9/AV1/VVC, 0~255 for AV1 NVENC/AMF.
+        /// The lower bound is at least 0 (a declared minimum of -1 means "auto").
+        /// When the option is missing or its declared maximum is unbounded (see <see cref="MaxMeaningfulQualityLimit"/>), returns 0~51,
+        /// the QP scale of H.264/HEVC 8-bit (x264/x265 CRF 0~51).
+        /// Reference: https://x265.readthedocs.io/en/master/cli.html (--crf 0..51.0)
+        /// </summary>
+        /// <param name="optionName">Name of the quality option in priv_data.</param>
+        private (int Min, int Max) GetQualityRange(string optionName)
+        {
+            const int fallbackMax = 51;
+
+            var option = ffmpeg.av_opt_find(_pCodecContext->priv_data, optionName, null, 0, 0);
+            if (option == null || !(option->max > 0 && option->max <= MaxMeaningfulQualityLimit))
+                return (0, fallbackMax);
+
+            var min = Math.Max(0, (int)Math.Ceiling(option->min));
+            var max = (int)Math.Floor(option->max);
+            return min <= max ? (min, max) : (0, fallbackMax);
+        }
+
         // ================================================================
         // Write Frame
         // ================================================================