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Fix audio-video sync issue in DASH MP4 muxer #13369

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Gautam-aman wants to merge 4 commits into from
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Fix audio-video sync issue in DASH MP4 muxer #13369

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23b3c42
Fix audio-video sync issue in DASH MP4 muxer by normalizing compositi…
Gautam-aman Mar 22, 2026
13697ee
Fix checkstyle violations: mark local variables as final
Gautam-aman Mar 22, 2026
47f0ed8
Fix checkstyle: make minPts variables final
Gautam-aman Mar 22, 2026
4c7c229
Fix checkstyle: make allSet computation compliant with final rule
Gautam-aman Mar 22, 2026
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58 changes: 52 additions & 6 deletions app/src/main/java/org/schabi/newpipe/streams/Mp4FromDashWriter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -162,6 +162,12 @@ public void build(final SharpStream output) throws IOException {
final int[] defaultMediaTime = new int[readers.length];
final int[] defaultSampleDuration = new int[readers.length];
final int[] sampleCount = new int[readers.length];
final long[] firstPts = new long[readers.length];
final boolean[] firstPtsSet = new boolean[readers.length];
final long[] basePts = new long[readers.length];
final boolean[] basePtsSet = new boolean[readers.length];
final boolean[] minPtsComputedArr = new boolean[]{false};
final long[] minPtsArr = new long[]{0};
Comment on lines +169 to +170
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@TobiGr TobiGr Mar 30, 2026 •
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Why are these two vars arrays? They both only hold one value.


final TablesInfo[] tablesInfo = new TablesInfo[tracks.length];
for (int i = 0; i < tablesInfo.length; i++) {
Expand Down Expand Up @@ -317,7 +323,7 @@ public void build(final SharpStream output) throws IOException {

for (int i = 0; i < readers.length; i++) {
if (sampleIndex[i] < 0) {
continue; // track is done
continue;
}

final long chunkOffset = writeOffset;
Expand All @@ -336,26 +342,66 @@ public void build(final SharpStream output) throws IOException {
if (sample == null) {
if (tablesInfo[i].ctts > 0 && sampleExtra[i] >= 0) {
writeEntryArray(tablesInfo[i].ctts, 1, sampleCount[i],
sampleExtra[i]); // flush last entries
sampleExtra[i]);
outRestore();
}
sampleIndex[i] = -1;
break;
}

// Normalize composition timestamps to align audio and video timelines
final long pts = sample.info.sampleCompositionTimeOffset;
if (!firstPtsSet[i]) {
firstPts[i] = pts;
firstPtsSet[i] = true;
}

if (!minPtsComputedArr[0]) {
final boolean allSet;
{
boolean temp = true;
for (int k = 0; k < readers.length; k++) {
if (!firstPtsSet[k]) {
temp = false;
break;
}
}
allSet = temp;
}
Comment on lines +360 to +370
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@TobiGr TobiGr Mar 30, 2026

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I don't understand your code here. Why do you introduce a temp var? Can't you set allSet = false directly? This should be equal to you code but is easier to understand:

Suggested change
final boolean allSet;
{
boolean temp = true;
for (int k = 0; k < readers.length; k++) {
if (!firstPtsSet[k]) {
temp = false;
break;
}
}
allSet = temp;
}
boolean allSet = true;
for (int k = 0; allSet && k < readers.length; k++) {
if (!firstPtsSet[k]) {
allSet = false;
}
}


if (allSet) {
minPtsArr[0] = firstPts[0];
for (int k = 1; k < readers.length; k++) {
minPtsArr[0] = Math.min(minPtsArr[0], firstPts[k]);
}
minPtsComputedArr[0] = true;
}
}

sampleIndex[i]++;

if (!basePtsSet[i]) {
if (minPtsComputedArr[0]) {
basePts[i] = minPtsArr[0];
} else {
basePts[i] = firstPts[i];
}
basePtsSet[i] = true;
}

final int correctedOffset = (int) (pts - basePts[i]);
if (tablesInfo[i].ctts > 0) {
if (sample.info.sampleCompositionTimeOffset == sampleExtra[i]) {
if (correctedOffset == sampleExtra[i]) {
sampleCount[i]++;
} else {
if (sampleExtra[i] >= 0) {
tablesInfo[i].ctts = writeEntryArray(tablesInfo[i].ctts, 2,
sampleCount[i], sampleExtra[i]);
tablesInfo[i].ctts = writeEntryArray(
tablesInfo[i].ctts, 2, sampleCount[i], sampleExtra[i]
);
outRestore();
}
sampleCount[i] = 1;
sampleExtra[i] = sample.info.sampleCompositionTimeOffset;
sampleExtra[i] = correctedOffset;
}
}

Expand Down
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