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Stream Opus transcode source and encoded output; removes last store-path OOM

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Source read via streamed vault open + bounded staging copy (index-only duration/extension); encoded output walked from a bounded stream (new OggOpusParser.WalkAsync, byte-identical to the buffer oracle) and stored via streaming vault write. Adds parity tests.
This commit is contained in:
daniel-c-harvey
2026-06-26 14:06:33 -04:00
parent c1f2cafd8b
commit 4351ae04be
4 changed files with 572 additions and 64 deletions
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DeepDrftContent/Processors/Opus/OggOpusParser.cs
+205 -41
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@@ -20,8 +20,27 @@ public sealed record OggOpusWalk(byte[] SetupHeaderBytes, OggOpusSeekIndex SeekI
/// to the nearest enclosing page start. No external dependency: the encoder (FFmpeg) produces the bytes;
/// this turns them into the seek artifact deterministically, so it is unit-testable without a codec.
/// </summary>
/// <remarks>
/// Two entry points share one <see cref="WalkState"/> page-processing core, so they produce byte-identical
/// output by construction (the project's parity-oracle convention, mirroring
/// <c>RmsLoudnessAlgorithm.Compute</c> over its accumulator):
/// <list type="bullet">
/// <item><see cref="Walk(ReadOnlySpan{byte})"/> — the whole-buffer overload, retained as the byte-identity
/// parity oracle for the streaming variant.</item>
/// <item><see cref="WalkAsync(System.IO.Stream,System.Threading.CancellationToken)"/> — the streaming
/// variant: walks the page structure from a forward stream in a bounded read buffer (one Ogg page at a
/// time), so peak managed memory is O(buffer + seek-index + setup-header), independent of file size.</item>
/// </list>
/// </remarks>
public static class OggOpusParser
{
/// <summary>
/// The largest a single Ogg page can be: header(27) + a full 255-entry segment table + the maximum
/// payload those segments can describe (255 × 255 bytes). The streaming read buffer is floored at this
/// so a complete page always fits, which means a short read on a page can only mean a truncated stream.
/// </summary>
private const int MaxOggPageSize = OggOpusConstants.OggPageHeaderSize + 255 + 255 * 255; // 65307
/// <summary>
/// Walks <paramref name="oggBytes"/> and produces the setup header + seek index, or null if the
/// bytes are not a recognisable Ogg Opus stream (no setup header, no audio pages, or truncated
@@ -30,15 +49,7 @@ public static class OggOpusParser
/// </summary>
public static OggOpusWalk? Walk(ReadOnlySpan<byte> oggBytes)
{
var setupHeaderEnd = -1;
var sawOpusHead = false;
var sawOpusTags = false;
ushort preSkip = 0;
var points = new List<OpusSeekPoint>();
ulong lastGranule = 0;
var nextBucketTime = 0.0;
var firstAudioPointTaken = false;
var state = new WalkState();
var offset = 0;
while (offset + OggOpusConstants.OggPageHeaderSize <= oggBytes.Length)
@@ -68,12 +79,160 @@ public static class OggOpusParser
var granule = BinaryPrimitives.ReadUInt64LittleEndian(
page.Slice(OggOpusConstants.GranulePositionOffset, 8));
state.AddPage(granule, payload, page.Slice(0, pageTotalSize), offset);
offset += pageTotalSize;
}
return state.Finish((ulong)oggBytes.Length);
}
/// <summary>
/// Streaming counterpart of <see cref="Walk(ReadOnlySpan{byte})"/>: walks the Ogg page structure from
/// a forward <paramref name="stream"/> in a bounded read buffer (one Ogg page at a time), producing a
/// byte-identical <see cref="OggOpusWalk"/> without ever holding the whole encoded file in memory.
/// Returns null on the same malformed/truncated conditions as the buffer overload — it does not throw
/// for bad input (only <see cref="OperationCanceledException"/> propagates on cancellation).
/// </summary>
public static Task<OggOpusWalk?> WalkAsync(Stream stream, CancellationToken cancellationToken = default)
=> WalkAsync(stream, MaxOggPageSize, cancellationToken);
/// <summary>
/// Buffer-size-parameterised core. <paramref name="bufferSize"/> is floored at
/// <see cref="MaxOggPageSize"/> so any single page always fits in the buffer; the absolute byte
/// cursor (<c>absoluteOffset</c>) advances as the window compacts, so recorded seek offsets stay
/// absolute even though the buffer holds only a small window at any instant.
/// </summary>
internal static async Task<OggOpusWalk?> WalkAsync(Stream stream, int bufferSize, CancellationToken cancellationToken)
{
var state = new WalkState();
var buffer = new byte[Math.Max(bufferSize, MaxOggPageSize)];
var len = 0; // valid bytes held at buffer[0..len]
long absoluteOffset = 0; // absolute stream position of buffer[0]
while (true)
{
// The buffer overload's loop guard requires a full fixed header before parsing a page; once
// fewer than that remain (and the stream is drained) it is the natural end of the stream.
if (len < OggOpusConstants.OggPageHeaderSize)
{
len += await FillAsync(stream, buffer, len, cancellationToken);
if (len < OggOpusConstants.OggPageHeaderSize)
break;
}
if (!buffer.AsSpan(0, 4).SequenceEqual(OggOpusConstants.CapturePattern))
return null;
var segmentCount = buffer[OggOpusConstants.PageSegmentCountOffset];
var segmentTableEnd = OggOpusConstants.OggPageHeaderSize + segmentCount;
if (len < segmentTableEnd)
{
len += await FillAsync(stream, buffer, len, cancellationToken);
if (len < segmentTableEnd)
return null; // truncated header
}
var payloadSize = 0;
for (var i = 0; i < segmentCount; i++)
payloadSize += buffer[OggOpusConstants.OggPageHeaderSize + i];
var pageTotalSize = segmentTableEnd + payloadSize;
if (len < pageTotalSize)
{
len += await FillAsync(stream, buffer, len, cancellationToken);
if (len < pageTotalSize)
return null; // truncated payload (page never fully arrived before EOF)
}
var page = buffer.AsSpan(0, pageTotalSize);
var granule = BinaryPrimitives.ReadUInt64LittleEndian(
page.Slice(OggOpusConstants.GranulePositionOffset, 8));
var payload = page.Slice(segmentTableEnd, payloadSize);
state.AddPage(granule, payload, page, absoluteOffset);
// Compact the consumed page off the front of the window; the absolute cursor advances by the
// exact page size so every offset the state records remains an absolute stream position.
var remaining = len - pageTotalSize;
if (remaining > 0)
Buffer.BlockCopy(buffer, pageTotalSize, buffer, 0, remaining);
len = remaining;
absoluteOffset += pageTotalSize;
}
return state.Finish((ulong)absoluteOffset + (ulong)len);
}
/// <summary>
/// Fills <paramref name="buffer"/> from <paramref name="offset"/> to its end, issuing as many reads as
/// needed until the buffer is full or the stream is exhausted. Returns the number of bytes added.
/// </summary>
private static async Task<int> FillAsync(Stream stream, byte[] buffer, int offset, CancellationToken ct)
{
var added = 0;
while (offset + added < buffer.Length)
{
var read = await stream.ReadAsync(buffer.AsMemory(offset + added, buffer.Length - offset - added), ct);
if (read == 0)
break;
added += read;
}
return added;
}
private static bool StartsWith(ReadOnlySpan<byte> payload, ReadOnlySpan<byte> signature) =>
payload.Length >= signature.Length && payload[..signature.Length].SequenceEqual(signature);
/// <summary>
/// The single page-processing core both <see cref="Walk(ReadOnlySpan{byte})"/> and
/// <see cref="WalkAsync(Stream,int,CancellationToken)"/> drive, page by page, in stream order. Holding
/// the setup-header + seek-index accumulation here is what makes the two entry points byte-identical
/// by construction: there is exactly one copy of the OpusHead/OpusTags detection, pre-skip correction,
/// t=0 anchoring, and 0.5 s bucketing logic.
/// </summary>
private sealed class WalkState
{
// The real setup (OpusHead + OpusTags pages) is a few KB; this cap bounds the streaming capture so
// a malformed head-without-tags stream cannot grow it unboundedly. A stream that exceeds it has no
// OpusTags within the cap, so no audio points are ever recorded and Finish returns null either way
// — the cap never changes the output of a stream that produces a non-null result.
private const int MaxSetupHeaderBytes = 8 * 1024 * 1024;
private bool _sawOpusHead;
private bool _sawOpusTags;
private ushort _preSkip;
private int _setupHeaderEnd = -1;
private bool _capturingSetup = true;
private readonly List<byte> _setupHeader = new();
private readonly List<OpusSeekPoint> _points = new();
private ulong _lastGranule;
private double _nextBucketTime;
private bool _firstAudioPointTaken;
/// <summary>
/// Processes one fully-framed page. <paramref name="pageBytes"/> is the whole page (header +
/// segment table + payload) for verbatim setup capture; <paramref name="absoluteOffset"/> is the
/// page's absolute start in the stream — the value recorded in the seek index.
/// </summary>
public void AddPage(ulong granule, ReadOnlySpan<byte> payload, ReadOnlySpan<byte> pageBytes, long absoluteOffset)
{
if (_capturingSetup)
{
if (_setupHeader.Count + pageBytes.Length > MaxSetupHeaderBytes)
_capturingSetup = false; // malformed: give up capture (result will be null without tags)
else
_setupHeader.AddRange(pageBytes);
}
// The setup pages carry no audio granule (OpusHead has granulepos 0; OpusTags too). They
// are the leading pages whose payload opens with the Opus magic signatures.
if (!sawOpusHead && StartsWith(payload, OggOpusConstants.OpusHeadSignature))
if (!_sawOpusHead && StartsWith(payload, OggOpusConstants.OpusHeadSignature))
{
sawOpusHead = true;
setupHeaderEnd = offset + pageTotalSize;
_sawOpusHead = true;
_setupHeaderEnd = (int)(absoluteOffset + pageBytes.Length);
// RFC 7845 §5.1 — OpusHead layout after the 8-byte "OpusHead" magic:
// [0] version (1 byte), [1] channel count (1 byte),
@@ -81,15 +240,17 @@ public static class OggOpusParser
// pre_skip is the number of decoder samples to discard before presenting audio;
// all granule→time conversions must subtract it (RFC 7845 §4.3).
if (payload.Length >= OggOpusConstants.OpusHeadMinSize)
preSkip = BinaryPrimitives.ReadUInt16LittleEndian(
_preSkip = BinaryPrimitives.ReadUInt16LittleEndian(
payload.Slice(OggOpusConstants.OpusHeadPreSkipOffset, 2));
}
else if (sawOpusHead && !sawOpusTags && StartsWith(payload, OggOpusConstants.OpusTagsSignature))
else if (_sawOpusHead && !_sawOpusTags && StartsWith(payload, OggOpusConstants.OpusTagsSignature))
{
sawOpusTags = true;
setupHeaderEnd = offset + pageTotalSize;
_sawOpusTags = true;
_setupHeaderEnd = (int)(absoluteOffset + pageBytes.Length);
// The setup header ends at the OpusTags page; stop capturing so audio pages never grow it.
_capturingSetup = false;
}
else if (sawOpusHead && sawOpusTags)
else if (_sawOpusHead && _sawOpusTags)
{
// Audio page. Record the first audio page unconditionally (the seek anchor at t=0),
// then one entry per 0.5 s bucket. A page with no end-granule (mid-packet continuation,
@@ -101,46 +262,49 @@ public static class OggOpusParser
// Use this corrected time for bucketing so that a stream with pre-skip 3840 (~80 ms)
// does not systematically offset every indexed time by that amount.
var correctedTime = Math.Max(0.0,
(granule - (double)preSkip) / OggOpusConstants.OpusSampleRate);
(granule - (double)_preSkip) / OggOpusConstants.OpusSampleRate);
if (!firstAudioPointTaken)
if (!_firstAudioPointTaken)
{
// Anchor the first seek point at corrected time = 0 by storing the granule as
// preSkip. This guarantees that a binary search for t=0 ("largest entry with
// corrected time ≤ 0") always resolves to the first audio page's byte offset —
// even when the real granule is slightly above preSkip due to encoder lead-in.
points.Add(new OpusSeekPoint(preSkip, (ulong)offset));
firstAudioPointTaken = true;
nextBucketTime = OggOpusConstants.SeekBucketSeconds;
_points.Add(new OpusSeekPoint(_preSkip, (ulong)absoluteOffset));
_firstAudioPointTaken = true;
_nextBucketTime = OggOpusConstants.SeekBucketSeconds;
}
else if (correctedTime >= nextBucketTime)
else if (correctedTime >= _nextBucketTime)
{
points.Add(new OpusSeekPoint(granule, (ulong)offset));
_points.Add(new OpusSeekPoint(granule, (ulong)absoluteOffset));
// Advance past every bucket this page crossed so a long page does not emit a
// backlog of entries; the next bucket is the first boundary strictly after it.
while (nextBucketTime <= correctedTime)
nextBucketTime += OggOpusConstants.SeekBucketSeconds;
while (_nextBucketTime <= correctedTime)
_nextBucketTime += OggOpusConstants.SeekBucketSeconds;
}
lastGranule = granule;
_lastGranule = granule;
}
}
offset += pageTotalSize;
}
if (!sawOpusHead || setupHeaderEnd < 0 || points.Count == 0)
return null;
/// <summary>
/// Produces the final walk, or null on the same conditions the buffer overload rejected:
/// no OpusHead, no captured setup header, or no audio seek points. <paramref name="totalByteLength"/>
/// is the full stream length, recorded for end-of-stream seek clamping.
/// </summary>
public OggOpusWalk? Finish(ulong totalByteLength)
{
if (!_sawOpusHead || _setupHeaderEnd < 0 || _points.Count == 0)
return null;
var setupHeader = oggBytes[..setupHeaderEnd].ToArray();
// RFC 7845 §4.3: total duration is also pre-skip-corrected, matching the time a listener
// experiences (the last audio page's corrected time, clamped to ≥ 0).
var totalDuration = Math.Max(0.0,
(lastGranule - (double)preSkip) / OggOpusConstants.OpusSampleRate);
var index = new OggOpusSeekIndex(points, totalDuration, (ulong)oggBytes.Length, preSkip);
return new OggOpusWalk(setupHeader, index);
var setupHeader = _setupHeader.ToArray();
// RFC 7845 §4.3: total duration is also pre-skip-corrected, matching the time a listener
// experiences (the last audio page's corrected time, clamped to ≥ 0).
var totalDuration = Math.Max(0.0,
(_lastGranule - (double)_preSkip) / OggOpusConstants.OpusSampleRate);
var index = new OggOpusSeekIndex(_points, totalDuration, totalByteLength, _preSkip);
return new OggOpusWalk(setupHeader, index);
}
}
private static bool StartsWith(ReadOnlySpan<byte> payload, ReadOnlySpan<byte> signature) =>
payload.Length >= signature.Length && payload[..signature.Length].SequenceEqual(signature);
}