72 lines
3.0 KiB
Dart
72 lines
3.0 KiB
Dart
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import 'dart:math';
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/// mpv's built-in `stream-buffer-size` default (128 KiB). Written back for
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/// opens that don't qualify for an enlarged ring so a reused player instance
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/// never carries one item's tuning into the next.
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const mpvDefaultStreamBufferBytes = 128 * 1024;
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/// QuickTime/MP4 muxer family. Apple capture muxers (iPhone recordings and
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/// friends) can store audio packets seconds away from coeval video packets —
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/// in bytes, seconds × video byterate — which makes ffmpeg's DTS-ordered
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/// reads ping-pong across the file. Over HTTP every ping-pong that escapes
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/// mpv's stream ring buffer is a byte seek, and ffmpeg's http layer drops and
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/// redials the connection on every seek, collapsing throughput. MKV is
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/// interleaved by spec and excluded.
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const poorlyInterleavedContainers = {'mp4', 'mov', 'm4v', '3gp', '3g2'};
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const minStreamRingBytes = 16 * 1024 * 1024;
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const maxStreamRingBytes = 128 * 1024 * 1024;
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/// Ring for QuickTime-family content whose bitrate the backend didn't report.
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const unknownBitrateStreamRingBytes = 64 * 1024 * 1024;
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/// Seconds of content bytes the ring should hold. mpv guarantees only half
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/// the ring as seek-back history, so 6s of bytes ⇒ ≥3s of guaranteed
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/// interleave-skew coverage (observed iPhone skew ~2.9s) before the
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/// power-of-two round-up adds headroom.
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const _streamRingContentSeconds = 6;
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int nextPowerOfTwo(int value) {
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var result = 1;
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while (result < value) {
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result <<= 1;
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}
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return result;
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}
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/// Heap-tier cap for the stream ring on Android, mirroring the demuxer
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/// auto-scaling tiers in video_player_screen.dart — mpv is the
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/// ExoPlayer-fallback engine there, which is exactly where low-RAM TV boxes
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/// land.
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int androidStreamRingCapBytes(int heapMB) {
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if (heapMB <= 0) return unknownBitrateStreamRingBytes;
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if (heapMB <= 256) return 32 * 1024 * 1024;
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if (heapMB <= 512) return 64 * 1024 * 1024;
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return maxStreamRingBytes;
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}
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/// mpv `stream-buffer-size` for a network direct play of [container] at
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/// [bitrateKbps] total bitrate, or null when mpv's 128 KiB default suffices.
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///
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/// The ring absorbs the demuxer's audio↔video byte alternation entirely in
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/// RAM so the underlying HTTP reads stay linear. The ring is fully allocated
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/// (power-of-two rounded) per stream, hence the container gate and bitrate
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/// scaling instead of a flat global value.
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int? networkStreamRingBytes({
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required String? container,
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required int? bitrateKbps,
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int maxBytes = maxStreamRingBytes,
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}) {
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if (container == null) return null;
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// Jellyfin may report ffmpeg demuxer alias lists ('mov,mp4,m4a,3gp,3g2,mj2').
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final tokens = container.toLowerCase().split(',').map((token) => token.trim());
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if (!tokens.any(poorlyInterleavedContainers.contains)) return null;
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final cap = max(minStreamRingBytes, min(maxBytes, maxStreamRingBytes));
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if (bitrateKbps == null || bitrateKbps <= 0) return min(unknownBitrateStreamRingBytes, cap);
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final bytesPerSecond = bitrateKbps * 1000 ~/ 8;
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final ring = nextPowerOfTwo(bytesPerSecond * _streamRingContentSeconds);
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return max(minStreamRingBytes, min(ring, cap));
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}
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