From 3b07c754f82448e8e09e724c49e9320b4f8f33e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Verstraeten?= <cedric@verstraeten.io>
Date: Mon, 18 May 2026 12:56:17 +0000
Subject: [PATCH] Revert "Force fragment flush on close keyframes"

This reverts commit 3d4e37dfb93a203ead2d1ea5f8d2d2750ccd6973.
---
 machinery/src/video/mp4.go               | 11 +--
 machinery/src/video/mp4_loopseam_test.go | 99 ------------------------
 2 files changed, 1 insertion(+), 109 deletions(-)
 delete mode 100644 machinery/src/video/mp4_loopseam_test.go

diff --git a/machinery/src/video/mp4.go b/machinery/src/video/mp4.go
index 938e2e3..bc7643d 100644
--- a/machinery/src/video/mp4.go
+++ b/machinery/src/video/mp4.go
@@ -32,15 +32,6 @@ const MacEpochOffset uint64 = 2082844800
 // resulting in ~3 second fragments (assuming a typical GOP interval).
 const FragmentDurationMs = 3000
 
-// MinNormalGOPMs is the minimum spacing we expect between two consecutive
-// IDRs of a healthy source (typical encoders produce IDRs every 1000ms or
-// more). When two keyframes arrive closer than this, we treat the second one
-// as an upstream restart/loop-seam and force a fresh fragment so the seam
-// IDR cannot end up as a mid-fragment sync sample. The check only runs when
-// the current fragment has not yet reached FragmentDurationMs, so it never
-// fires during normal multi-GOP fragments at intended GOP boundaries.
-const MinNormalGOPMs = 950
-
 type MP4 struct {
 	// FileName is the name of the file
 	FileName                string
@@ -330,7 +321,7 @@ func (mp4 *MP4) AddSampleToTrack(trackID uint32, isKeyframe bool, data []byte, p
 		// seam IDR into its own fragment so each fragment stays a clean GOP.
 		if !shouldFlush && trackID == uint32(mp4.VideoTrack) && mp4.Start &&
 			mp4.LastKeyframeRawPTS > 0 && pts > mp4.LastKeyframeRawPTS &&
-			pts-mp4.LastKeyframeRawPTS < MinNormalGOPMs {
+			pts-mp4.LastKeyframeRawPTS < 500 {
 			log.Log.Warning(fmt.Sprintf("mp4.AddSampleToTrack(): forcing fragment flush at unexpectedly close keyframe (gap=%d ms, fragment elapsed=%d ms) - likely upstream loop/restart discontinuity", pts-mp4.LastKeyframeRawPTS, elapsed))
 			shouldFlush = true
 		}
diff --git a/machinery/src/video/mp4_loopseam_test.go b/machinery/src/video/mp4_loopseam_test.go
deleted file mode 100644
index 6c24812..0000000
--- a/machinery/src/video/mp4_loopseam_test.go
+++ /dev/null
@@ -1,99 +0,0 @@
-package video
-
-import (
-	"fmt"
-	"os"
-	"testing"
-
-	mp4ff "github.com/Eyevinn/mp4ff/mp4"
-	"github.com/kerberos-io/agent/machinery/src/models"
-)
-
-// TestMP4LoopSeamIsolation reproduces the loop-seam pattern from the
-// failing virtual-rtsp recordings: ~1s GOPs, but at the source-MP4
-// loop boundary an IDR arrives prematurely (~200-870ms after the
-// previous IDR). Without the fix this seam IDR ends up bunched into
-// the same fragment as the prior GOP's IDR which trips macOS
-// VideoToolbox (kVTVideoDecoderBadDataErr / -12909). The fix forces
-// a fragment flush whenever two IDRs arrive closer than MinNormalGOPMs.
-func TestMP4LoopSeamIsolation(t *testing.T) {
-	tmpFile := "/tmp/test_loop_seam.mp4"
-	defer os.Remove(tmpFile)
-
-	sps := []byte{0x67, 0x42, 0xc0, 0x1e, 0xd9, 0x00, 0xa0, 0x47, 0xfe, 0xc8}
-	pps := []byte{0x68, 0xce, 0x38, 0x80}
-	mp4Video := NewMP4(tmpFile, [][]byte{sps}, [][]byte{pps}, nil, 30)
-	mp4Video.SetWidth(1920)
-	mp4Video.SetHeight(1080)
-	v := mp4Video.AddVideoTrack("H264")
-
-	mk := func(k bool) []byte {
-		nt := byte(0x01)
-		if k {
-			nt = 0x65
-		}
-		f := []byte{0, 0, 0, 1, nt}
-		for i := 0; i < 200; i++ {
-			f = append(f, byte(i))
-		}
-		return f
-	}
-
-	frameDur := uint64(33)
-	pts := uint64(0)
-	emit := func(n int, gopLen int) {
-		for f := 0; f < n; f++ {
-			isKey := (f % gopLen) == 0
-			mp4Video.AddSampleToTrack(v, isKey, mk(isKey), pts)
-			pts += frameDur
-		}
-	}
-
-	// 17 seconds of normal content (last "good" IDR at sec 17).
-	emit(17*30, 30)
-	// Seam: IDR arrives ~867ms after previous (vs normal 1000ms).
-	pts -= 100
-	emit(13*30, 30)
-
-	mp4Video.Close(&models.Config{Signing: &models.Signing{PrivateKey: ""}})
-
-	f, _ := os.Open(tmpFile)
-	defer f.Close()
-	parsed, err := mp4ff.DecodeFile(f)
-	if err != nil {
-		t.Fatalf("decode: %v", err)
-	}
-
-	fragIdx := 0
-	for _, seg := range parsed.Segments {
-		for _, fr := range seg.Fragments {
-			for _, traf := range fr.Moof.Trafs {
-				if traf.Tfhd.TrackID != 1 {
-					continue
-				}
-				tfdt := traf.Tfdt.BaseMediaDecodeTime()
-				offset := uint64(0)
-				var keys []uint64
-				for _, trun := range traf.Truns {
-					for _, s := range trun.Samples {
-						if (s.Flags>>24)&0x03 == 0x02 {
-							keys = append(keys, offset)
-						}
-						offset += uint64(s.Dur)
-					}
-				}
-				fmt.Printf("frag %d tfdt=%d samples_dur=%d keys@%v\n",
-					fragIdx, tfdt, offset, keys)
-				for i := 1; i < len(keys); i++ {
-					gap := keys[i] - keys[i-1]
-					if gap < MinNormalGOPMs {
-						t.Errorf("frag %d (tfdt=%d): two IDRs only %d ms apart "+
-							"in same fragment (< %d) - seam was not isolated",
-							fragIdx, tfdt, gap, MinNormalGOPMs)
-					}
-				}
-				fragIdx++
-			}
-		}
-	}
-}