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77 lines
2.8 KiB
77 lines
2.8 KiB
using System;
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using System.Collections.Generic;
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using System.IO;
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using Jellyfin.MediaEncoding.Keyframes.Matroska.Extensions;
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using NEbml.Core;
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namespace Jellyfin.MediaEncoding.Keyframes.Matroska
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{
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/// <summary>
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/// The keyframe extractor for the matroska container.
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/// </summary>
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public static class MatroskaKeyframeExtractor
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{
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/// <summary>
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/// Extracts the keyframes in ticks (scaled using the container timestamp scale) from the matroska container.
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/// </summary>
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/// <param name="filePath">The file path.</param>
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/// <returns>An instance of <see cref="KeyframeData"/>.</returns>
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public static KeyframeData GetKeyframeData(string filePath)
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{
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using var stream = File.OpenRead(filePath);
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using var reader = new EbmlReader(stream);
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var seekHead = reader.ReadSeekHead();
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var info = reader.ReadInfo(seekHead.InfoPosition);
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var videoTrackNumber = reader.FindFirstTrackNumberByType(seekHead.TracksPosition, MatroskaConstants.TrackTypeVideo);
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var keyframes = new List<long>();
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reader.ReadAt(seekHead.CuesPosition);
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reader.EnterContainer();
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while (reader.FindElement(MatroskaConstants.CuePoint))
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{
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reader.EnterContainer();
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ulong? trackNumber = null;
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// Mandatory element
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reader.FindElement(MatroskaConstants.CueTime);
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var cueTime = reader.ReadUInt();
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// Mandatory element
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reader.FindElement(MatroskaConstants.CueTrackPositions);
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reader.EnterContainer();
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if (reader.FindElement(MatroskaConstants.CuePointTrackNumber))
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{
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trackNumber = reader.ReadUInt();
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}
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reader.LeaveContainer();
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if (trackNumber == videoTrackNumber)
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{
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keyframes.Add(ScaleToTicks(cueTime, info.TimestampScale));
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}
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reader.LeaveContainer();
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}
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reader.LeaveContainer();
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var result = new KeyframeData(ScaleToTicks(info.Duration ?? 0, info.TimestampScale), keyframes);
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return result;
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}
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private static long ScaleToTicks(ulong unscaledValue, long timestampScale)
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{
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// TimestampScale is in nanoseconds, scale it to get the value in ticks, 1 tick == 100 ns
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return (long)unscaledValue * timestampScale / 100;
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}
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private static long ScaleToTicks(double unscaledValue, long timestampScale)
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{
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// TimestampScale is in nanoseconds, scale it to get the value in ticks, 1 tick == 100 ns
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return Convert.ToInt64(unscaledValue * timestampScale / 100);
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}
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}
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}
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