Upgrade Version

.gitignore

@@ -48,3 +48,4 @@ desktop.ini
 
 # Developer Utility Files
 /REVIEW_CHECKLIST.md
+/REVIEW_FFMPEG.md

RenderMod.cs

@@ -9,7 +9,7 @@ using MelonLoader.Utils;
 using UnityEngine;
 using Object = UnityEngine.Object;
 
-[assembly: MelonInfo(typeof(RenderMod), "ADOFAI Renderer", "0.2.6-INDEV", "ADOFAI Editor Forum")]
+[assembly: MelonInfo(typeof(RenderMod), "ADOFAI Renderer", "0.2.7-INDEV", "ADOFAI Editor Forum")]
 [assembly: MelonGame("7th Beat Games", "A Dance of Fire and Ice")]
 
 namespace ADOFAIRenderer;

Util/FFmpeg/FFmpegNativeDecoder.cs

@@ -191,6 +191,13 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
     private bool _isOpened;
     private bool _disposed;
     private bool _isDraining;
+
+    /// <summary>Number of video packets skipped because the decoder rejected them as invalid data.</summary>
+    private int _skippedPacketCount;
+
+    /// <summary>Number of skipped packets for which a warning is logged.</summary>
+    private const int MaxLoggedSkippedPackets = 5;
+
     private readonly object _lock = new();
 
     // Fields to detect SwsContext updates
@@ -371,6 +378,16 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
                 if (_videoStreamIndex == -1)
                     throw new Exception("Failed to find video stream.");
 
+                // Only the video stream is used. The demuxer does not need to return the packets of the other streams
+                // (audio, subtitles, ...) once they are marked as discarded.
+                // Reference: AVStream.discard - "Selects which packets can be discarded at will and do not need to be demuxed."
+                // https://ffmpeg.org/doxygen/trunk/structAVStream.html
+                for (int i = 0; i < _pFormatContext->nb_streams; i++)
+                {
+                    if (i != _videoStreamIndex)
+                        _pFormatContext->streams[i]->discard = AVDiscard.AVDISCARD_ALL;
+                }
+
                 var stream = _pFormatContext->streams[_videoStreamIndex];
                 _timeBase = stream->time_base;
 
@@ -441,9 +458,13 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
                     TotalFrames = 0;
                 }
 
-                Duration = _pFormatContext->duration > 0
-                    ? _pFormatContext->duration / (double)ffmpeg.AV_TIME_BASE
-                    : (stream->duration > 0 ? stream->duration * ffmpeg.av_q2d(stream->time_base) : 0);
+                // Duration of the video stream (AVStream.duration, in the stream time base).
+                // When the stream does not carry a duration, the container duration (AVFormatContext.duration,
+                // in AV_TIME_BASE units, the longest of all streams) is used.
+                // Reference: https://ffmpeg.org/doxygen/trunk/structAVStream.html, https://ffmpeg.org/doxygen/trunk/structAVFormatContext.html
+                Duration = stream->duration > 0
+                    ? stream->duration * ffmpeg.av_q2d(stream->time_base)
+                    : _pFormatContext->duration > 0 ? _pFormatContext->duration / (double)ffmpeg.AV_TIME_BASE : 0;
 
                 // 9. Allocate frame and packet buffers
                 // Reference: https://ffmpeg.org/doxygen/trunk/group__lavu__frame.html
@@ -655,6 +676,8 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
     /// <summary>
     /// Reads packets from the container until a packet belonging to the video stream is found,
     /// then sends it to the decoder via <c>avcodec_send_packet</c>.
+    /// A packet that the decoder rejects as invalid data (<c>AVERROR_INVALIDDATA</c>, e.g. a damaged packet)
+    /// is skipped and the next packet is read. Any other decoder error is thrown.
     /// Reference: https://ffmpeg.org/doxygen/trunk/group__lavc__encdec.html
     /// </summary>
     /// <returns>True if a video packet was sent; false on EOF.</returns>
@@ -670,6 +693,18 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
             {
                 ret = ffmpeg.avcodec_send_packet(_pCodecContext, _pPacket);
                 ffmpeg.av_packet_unref(_pPacket);
+
+                if (ret == ffmpeg.AVERROR_INVALIDDATA)
+                {
+                    // The warning is logged for the first few packets only (a damaged file can have many).
+                    _skippedPacketCount++;
+                    if (_skippedPacketCount <= MaxLoggedSkippedPackets)
+                    {
+                        Melon<RenderMod>.Logger.Warning($"[FFmpegNativeDecoder] Skipped an invalid video packet ({_skippedPacketCount}): {GetFFmpegErrorString(ret)}");
+                    }
+                    continue;
+                }
+
                 if (ret < 0)
                 {
                     throw new Exception($"Error sending packet to decoder: {GetFFmpegErrorString(ret)}");
@@ -1212,107 +1247,24 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
     // ──────────────────────────────────────────────────────────────
 
     /// <summary>
-    /// Decodes and discards a specified number of frames immediately without GPU-to-CPU transfer overhead.
+    /// Maximum distance in frames over which <see cref="SeekToTime"/> moves forward by decoding.
+    /// Decoding forward needs no keyframe seek and no decoder flush, which is cheaper than seeking for short distances.
     /// </summary>
-    /// <param name="count">Number of frames to discard.</param>
-    private void SkipFrames(int count)
-    {
-        lock (_lock)
-        {
-            if (!_isOpened || _disposed) return;
-            if (count <= 0) return;
-
-            int skipped = 0;
-            if (_hasCachedFrame)
-            {
-                ffmpeg.av_frame_unref(_pCachedFrame);
-                _hasCachedFrame = false;
-                skipped++;
-            }
-
-            while (skipped < count)
-            {
-                int ret = ffmpeg.avcodec_receive_frame(_pCodecContext, _pDecodedFrame);
-                if (ret == 0)
-                {
-                    GetTimestampAndUpdateIndex(_pDecodedFrame);
-                    ffmpeg.av_frame_unref(_pDecodedFrame);
-                    skipped++;
-                    continue;
-                }
-
-                if (ret == ffmpeg.AVERROR(ffmpeg.EAGAIN))
-                {
-                    if (_isDraining) break;
-
-                    if (!ReadAndSendPacket())
-                    {
-                        _isDraining = true;
-                        ffmpeg.avcodec_send_packet(_pCodecContext, null);
-                    }
-                }
-                else if (ret == ffmpeg.AVERROR_EOF)
-                {
-                    break;
-                }
-                else
-                {
-                    throw new Exception($"Error skipping frames: {GetFFmpegErrorString(ret)}");
-                }
-            }
-        }
-    }
+    private const int MaxForwardDecodeFrames = 60;
 
     /// <summary>
-    /// Seeks to a specific playback time in seconds using backward keyframe seek followed by forward decode.
-    /// Intermediate frames are discarded without GPU-to-host memory transfer to maximize seek speed;
-    /// only the target frame is transferred and preserved in <see cref="_pCachedFrame"/>.
+    /// Decodes forward from the current decoder position until the first frame whose presentation time is at least
+    /// <paramref name="timeSeconds"/> minus half a frame, and keeps that frame in <see cref="_pCachedFrame"/>
+    /// for the next <c>TryRead*</c> call.
+    /// Frames before the target are discarded without GPU-to-host memory transfer; only the target frame is transferred.
+    /// When the end of the stream is reached before the target, no frame is cached.
     /// </summary>
-    /// <param name="timeSeconds">Target time in seconds to seek to.</param>
-    public void SeekToTime(double timeSeconds)
+    /// <param name="timeSeconds">Target time in seconds.</param>
+    private void DecodeToTarget(double timeSeconds)
     {
-        lock (_lock)
-        {
-            if (!_isOpened || _disposed) return;
-
-            if (timeSeconds < 0) timeSeconds = 0;
-            double targetFrameIndex = timeSeconds * FPS;
-
-            // If already at target index or very close future, skip frames instead of seek to avoid I-frame seek latency
-            bool useSkip = targetFrameIndex >= _currentFrameIndex && targetFrameIndex - _currentFrameIndex < 60;
-            if (useSkip)
-            {
-                SkipFrames((int)(targetFrameIndex - _currentFrameIndex));
-                return;
-            }
-
-            if (_hasCachedFrame)
-            {
-                ffmpeg.av_frame_unref(_pCachedFrame);
-                _hasCachedFrame = false;
-            }
-
-            long targetPts = (long)Math.Round(timeSeconds / ffmpeg.av_q2d(_timeBase));
-            int ret = ffmpeg.av_seek_frame(_pFormatContext, _videoStreamIndex, targetPts, ffmpeg.AVSEEK_FLAG_BACKWARD);
-            if (ret < 0)
-            {
-                // Fallback to beginning of file on seek failure
-                ret = ffmpeg.av_seek_frame(_pFormatContext, _videoStreamIndex, 0, ffmpeg.AVSEEK_FLAG_BACKWARD);
-                if (ret < 0)
-                {
-                    throw new Exception($"Seek failed: {GetFFmpegErrorString(ret)}");
-                }
-            }
-
-            // Flush decoder internal buffers
-            // Reference: https://ffmpeg.org/doxygen/trunk/group__lavc__encdec.html
-            ffmpeg.avcodec_flush_buffers(_pCodecContext);
-            _isDraining = false;
-
-            // Decode frames until reaching the target presentation timestamp
         while (true)
         {
-                ret = ffmpeg.avcodec_receive_frame(_pCodecContext, _pDecodedFrame);
+            int ret = ffmpeg.avcodec_receive_frame(_pCodecContext, _pDecodedFrame);
             if (ret == 0)
             {
                 double currentPts = GetFrameTimestamp(_pDecodedFrame);
@@ -1343,28 +1295,18 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
                     }
 
                     _hasCachedFrame = true;
-                        break;
+                    return;
                 }
 
                 // Discard non-matching intermediate frame without transferring to CPU
-                    long ptsValue = _pDecodedFrame->best_effort_timestamp != ffmpeg.AV_NOPTS_VALUE
-                        ? _pDecodedFrame->best_effort_timestamp
-                        : _pDecodedFrame->pts;
-                    if (ptsValue == ffmpeg.AV_NOPTS_VALUE)
-                    {
-                        _currentFrameIndex++;
-                    }
-                    else
-                    {
-                        _currentFrameIndex = (long)Math.Round(currentPts * FPS);
-                    }
+                GetTimestampAndUpdateIndex(_pDecodedFrame);
                 ffmpeg.av_frame_unref(_pDecodedFrame);
                 continue;
             }
 
             if (ret == ffmpeg.AVERROR(ffmpeg.EAGAIN))
             {
-                    if (_isDraining) break;
+                if (_isDraining) return;
 
                 if (!ReadAndSendPacket())
                 {
@@ -1374,7 +1316,7 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
             }
             else if (ret == ffmpeg.AVERROR_EOF)
             {
-                    break;
+                return;
             }
             else
             {
@@ -1382,6 +1324,87 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
             }
         }
     }
+
+    /// <summary>
+    /// Moves the playback position to a time in seconds.
+    /// The next <c>TryRead*</c> call returns the first frame whose presentation time is at least
+    /// <paramref name="timeSeconds"/> minus half a frame (the frame nearest to the target time).
+    /// Both paths below return that same frame:
+    ///   - Forward decode: the target is ahead of the current position by less than <see cref="MaxForwardDecodeFrames"/> frames.
+    ///     Frames are decoded and discarded up to the target.
+    ///   - Keyframe seek: all other cases (target before the current position, far ahead, or the target frame already read).
+    ///     A backward keyframe seek is followed by a forward decode up to the target.
+    /// The target frame is transferred and preserved in <see cref="_pCachedFrame"/>; when it is already there, nothing is decoded.
+    /// </summary>
+    /// <param name="timeSeconds">Target time in seconds to seek to.</param>
+    public void SeekToTime(double timeSeconds)
+    {
+        lock (_lock)
+        {
+            if (!_isOpened || _disposed) return;
+
+            if (timeSeconds < 0) timeSeconds = 0;
+
+            // Earliest presentation time that satisfies the target (target minus half a frame).
+            double threshold = timeSeconds - (0.5 / FPS);
+
+            // Index of the first frame that satisfies the target. The epsilon keeps a frame that lies exactly on the
+            // margin from being excluded by floating point rounding.
+            double targetFrameIndex = Math.Ceiling(timeSeconds * FPS - 0.5 - 1e-6);
+
+            if (_hasCachedFrame)
+            {
+                // A frame is already positioned for the next read (e.g. by a previous SeekToTime call).
+                double cachedPts = GetFrameTimestamp(_pCachedFrame);
+                if (cachedPts >= threshold)
+                {
+                    // The cached frame is the first frame that satisfies the target.
+                    // When the target lies before it, the frames in between are no longer available and a keyframe seek is required.
+                    if (cachedPts - threshold < 1.0 / FPS) return;
+                }
+                else if (targetFrameIndex - _currentFrameIndex < MaxForwardDecodeFrames)
+                {
+                    // The cached frame lies before the target: drop it and continue decoding forward.
+                    GetTimestampAndUpdateIndex(_pCachedFrame);
+                    ffmpeg.av_frame_unref(_pCachedFrame);
+                    _hasCachedFrame = false;
+                    DecodeToTarget(timeSeconds);
+                    return;
+                }
+            }
+            else if (targetFrameIndex > _currentFrameIndex && targetFrameIndex - _currentFrameIndex < MaxForwardDecodeFrames)
+            {
+                // The target frame has not been read yet and is close: decode forward instead of seeking.
+                DecodeToTarget(timeSeconds);
+                return;
+            }
+
+            if (_hasCachedFrame)
+            {
+                ffmpeg.av_frame_unref(_pCachedFrame);
+                _hasCachedFrame = false;
+            }
+
+            long targetPts = (long)Math.Round(timeSeconds / ffmpeg.av_q2d(_timeBase));
+            int ret = ffmpeg.av_seek_frame(_pFormatContext, _videoStreamIndex, targetPts, ffmpeg.AVSEEK_FLAG_BACKWARD);
+            if (ret < 0)
+            {
+                // Fallback to beginning of file on seek failure
+                ret = ffmpeg.av_seek_frame(_pFormatContext, _videoStreamIndex, 0, ffmpeg.AVSEEK_FLAG_BACKWARD);
+                if (ret < 0)
+                {
+                    throw new Exception($"Seek failed: {GetFFmpegErrorString(ret)}");
+                }
+            }
+
+            // Flush decoder internal buffers
+            // Reference: https://ffmpeg.org/doxygen/trunk/group__lavc__encdec.html
+            ffmpeg.avcodec_flush_buffers(_pCodecContext);
+            _isDraining = false;
+
+            // Decode frames until reaching the target presentation timestamp
+            DecodeToTarget(timeSeconds);
+        }
     }
 
     /// <summary>

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>
@@ -723,6 +723,16 @@ namespace ADOFAIRenderer.Util.FFmpeg
                     if (ffmpeg.avcodec_parameters_from_context(_pVideoStream->codecpar, _pCodecContext) < 0)
                         throw new Exception("Failed to copy codec parameters to stream.");
 
+                    // Stream time base: unit of the timestamps stored in the container.
+                    // Set to the codec time base (1 / framerate) so that every frame interval is a whole number of ticks.
+                    // When it is left unset, the muxer uses 1/90000, in which the interval of rates such as
+                    // 59.94 fps (1501.5 ticks), 23.976 fps (3753.75 ticks) or 165 fps (545.45 ticks) is not an integer,
+                    // and the frame durations alternate between two values.
+                    // The muxer may still adjust the value in avformat_write_header (e.g. mp4 scales it to at least 10000);
+                    // packet timestamps are rescaled to the final value in SendFrameAndWritePackets.
+                    // Reference: https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/mux.c (init_muxer: default 1/90000)
+                    _pVideoStream->time_base = _pCodecContext->time_base;
+
                     // ── Step 4.5 (Optional): Initialize audio stream ──
                     // If EncoderSettings.Audio is set, add audio stream.
                     if (_settings.Audio.HasValue)
@@ -825,7 +835,7 @@ 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 +857,21 @@ 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
-                        // NAL HRD (Hypothetical Reference Decoder) specification. May be required for streaming compatibility.
-                        if (encoder == VideoEncoder.Libx264 || encoder == VideoEncoder.Libx265)
+                        // HRD (Hypothetical Reference Decoder) signaling for CBR output, used for streaming compatibility.
+                        //   libx264: "nal-hrd=cbr" writes the NAL HRD information and pads filler data to keep the bitrate constant.
+                        //            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 +895,77 @@ 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);
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "qp_p", qpValue.ToString(), 0);
+                        TrySetOption("qp_i", qpValue.ToString());
+                        TrySetOption("qp_p", qpValue.ToString());
                     }
                     else if (encoder.Kind == EncoderKind.QSV)
                     {
-                        // QSV: Uses ICQ (Intelligent Constant Quality) mode with "global_quality" option
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "global_quality", qpValue.ToString(), 0);
+                        // QSV: ICQ (Intelligent Constant Quality) mode, configured with AVCodecContext.global_quality.
+                        _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.
-                        ffmpeg.av_opt_set(_pCodecContext->priv_data, "crf", qpValue.ToString(), 0);
+                        // Range: 0 (lossless) ~ 51 (lowest quality) for x264/x265, 0~63 for VP9/AV1. Typically between 18 and 28.
+                        TrySetOption("crf", qpValue.ToString());
                     }
                     break;
                 default:
@@ -914,6 +973,49 @@ 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
         // ================================================================