# \[Bug + patch\] UMP-\>bytestream translator delivers a single-packet SysEx7 with a zero or stale timestamp (8.0.12, develop 9.0.1) **URL:** \ **Category:** MacOSX and iOS\ **Created:** [August 21, 2026, 2:29am UTC](https://forum.juce.com/t/bug-patch-ump-bytestream-translator-delivers-a-single-packet-sysex7-with-a-zero-or-stale-timestamp-8-0-12-develop-9-0-1/69351 "2026-08-21T02:29:39Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![jos-ccrma](https://avatars.discourse-cdn.com/v4/letter/j/90ced4/32.png) [@jos-ccrma](https://forum.juce.com/u/jos-ccrma)\ **Post date:** [August 21, 2026, 2:29am UTC](https://forum.juce.com/t/bug-patch-ump-bytestream-translator-delivers-a-single-packet-sysex7-with-a-zero-or-stale-timestamp-8-0-12-develop-9-0-1/69351/1 "2026-08-21T02:29:39Z")
**Summary.** `SingleGroupMidi1ToBytestreamTranslator::dispatch()` (modules/juce\_audio\_basics/midi/ump/juce\_UMPMidi1ToBytestreamTranslator.h) captures the packet time into `pendingSysExTime` only in its `ongoingSysex` branch. A SysEx short enough to fit one UMP packet is `SysEx7::Kind::complete`, which the extractor reports directly as `lastSysex`, so the time is never captured and the message is delivered with whatever `pendingSysExTime` last held: `0.0` on a fresh translator, or – since only `reset()` clears it – the timestamp of the previous multi-packet SysEx. Present in 8.0.12 and unchanged on `develop` at dcf6bba08d (9.0.1). **How it shows up.** Any SysEx of up to six data bytes. Mine was `F0 00 00 66 14 00 F7` – a Mackie / Logic Control device query that a Mac control-surface scan sends to every MIDI destination, arriving at an iPad over IDAM. An iOS standalone plugin auto-opens every MIDI input (`shouldAutoOpenMidiDevices` defaults to true), and `AudioProcessorPlayer::handleIncomingMidiMessage` passes the message to `MidiMessageCollector::addMessageToQueue` unstamped, which trips ```auto jassert (! approximatelyEqual (message.getTimeStamp(), 0.0)); ``` In a Release build there is no crash, but the arithmetic is still wrong: `sampleNumber = (0 - 0.001 * lastCallbackTime) * sampleRate` is large and negative, so the “older than a second” guard (`sampleNumber > sampleRate`) can never fire, and `removeNextBlockOfMessages()` clamps the message to sample 0 instead of dropping it. The stale case is quieter: a short SysEx after a long one is simply timed as the earlier message. **Fix.** Mirror the guard the `ongoingSysex` branch already has: ```cpp case SysexExtractorCallbackKind::lastSysex: { if (pendingSysExData.empty()) pendingSysExTime = time; pendingSysExData.insert (pendingSysExData.end(), bytes.begin(), bytes.end()); ... ``` **Test.** The attached patch also adds a case to `UniversalMidiPacketTests` in juce\_UMP\_test.cpp, “Single-packet SysEx7 messages carry the packet’s own timestamp”: it dispatches the query above as one packet at t=123.456 and expects 123.456; a start+end pair at 10.0/10.5 and expects 10.0 (first packet’s time – unchanged behaviour); the single packet again at 20.0 and expects 20.0; and a MIDI clock at 77.25 and expects 77.25 (real-time messages take the `notSysex` path and were never affected). Against unpatched `develop` the new case fails exactly twice – ```auto Expected value: 123.456, Actual value: 0 Expected value: 20, Actual value: 10 ``` -- and with the one-line fix the whole “Universal MIDI Packet” test is 1706 passes, 0 failures. Same results on 8.0.12. **Patch** against `develop` (dcf6bba08d) – `git apply` from the repo root. Happy to open a PR instead if that is preferred. ```diff diff --git a/modules/juce_audio_basics/midi/ump/juce_UMPMidi1ToBytestreamTranslator.h b/modules/juce_audio_basics/midi/ump/juce_UMPMidi1ToBytestreamTranslator.h index 7715b0919e..41e5856429 100644 --- a/modules/juce_audio_basics/midi/ump/juce_UMPMidi1ToBytestreamTranslator.h +++ b/modules/juce_audio_basics/midi/ump/juce_UMPMidi1ToBytestreamTranslator.h @@ -274,6 +274,17 @@ public: case SysexExtractorCallbackKind::lastSysex: { + // A SysEx that fits in a single UMP packet (SysEx7::Kind::complete) never + // passes through the ongoingSysex branch, so without this the message + // would be delivered with whatever pendingSysExTime last held: 0.0 on a + // fresh translator (tripping the timestamp assertion in + // MidiMessageCollector::addMessageToQueue), or -- since only reset() + // clears it -- the timestamp of the PREVIOUS multi-packet SysEx. + // Covered by "Single-packet SysEx7 messages carry the packet's own + // timestamp" in juce_UMP_test.cpp. + if (pendingSysExData.empty()) + pendingSysExTime = time; + pendingSysExData.insert (pendingSysExData.end(), bytes.begin(), bytes.end()); if (pendingSysExData.empty()) diff --git a/modules/juce_audio_basics/midi/ump/juce_UMP_test.cpp b/modules/juce_audio_basics/midi/ump/juce_UMP_test.cpp index 8a583189a7..afcd254fd6 100644 --- a/modules/juce_audio_basics/midi/ump/juce_UMP_test.cpp +++ b/modules/juce_audio_basics/midi/ump/juce_UMP_test.cpp @@ -168,6 +168,65 @@ public: } } + beginTest ("Single-packet SysEx7 messages carry the packet's own timestamp"); + { + // A SysEx that fits in one UMP packet is SysEx7::Kind::complete, which the + // bytestream translator reports straight to its lastSysex branch. That + // branch used to leave pendingSysExTime alone (only ongoingSysex wrote it), + // so the message went out stamped with whatever the member last held: 0.0 + // on a fresh translator, or -- since only reset() clears it -- the time of + // the previous multi-packet SysEx. + SingleGroupMidi1ToBytestreamTranslator translator (0); + + struct Delivered { MidiMessage message; double time; }; + std::vector delivered; + + const auto collect = [&] (const BytesOnGroup& b, double t) + { + delivered.push_back ({ makeMidiMessage (b, t), t }); + }; + + const auto lastTime = [&] { return delivered.empty() ? -1.0 : delivered.back().time; }; + + // F0 00 00 66 14 00 F7 -- a Mackie / Logic Control device query. Five data + // bytes fit one SysEx7 packet. + const std::byte query[] { std::byte { 0x00 }, std::byte { 0x00 }, std::byte { 0x66 }, + std::byte { 0x14 }, std::byte { 0x00 } }; + const auto single = Factory::makeSysExIn1Packet (0, Span (query, std::size (query))); + + translator.dispatch (View { single.data() }, 123.456, collect); + expectEquals ((int) delivered.size(), 1); + expect (! delivered.empty() && delivered.back().message.isSysEx()); + expect (! delivered.empty() && delivered.back().message.getRawDataSize() == 7); + expectEquals (lastTime(), 123.456); + + // A multi-packet SysEx keeps its FIRST packet's time, as it always did... + const std::byte longData[] { std::byte { 0x01 }, std::byte { 0x02 }, std::byte { 0x03 }, std::byte { 0x04 }, + std::byte { 0x05 }, std::byte { 0x06 }, std::byte { 0x07 }, std::byte { 0x08 } }; + const auto start = Factory::makeSysExStart (0, Span (longData, 6)); + const auto end = Factory::makeSysExEnd (0, Span (longData + 6, 2)); + + translator.dispatch (View { start.data() }, 10.0, collect); + translator.dispatch (View { end.data() }, 10.5, collect); + expectEquals ((int) delivered.size(), 2); + expect (! delivered.empty() && delivered.back().message.getRawDataSize() == 10); + expectEquals (lastTime(), 10.0); + + // ...and a single-packet SysEx after it is stamped with its own time, not + // the previous message's. + translator.dispatch (View { single.data() }, 20.0, collect); + expectEquals ((int) delivered.size(), 3); + expectEquals (lastTime(), 20.0); + + // Real-time messages were never affected: they take the notSysex path, + // which passes the time straight through. + const auto clock = Factory::makeTimingClock (0); + translator.dispatch (View { clock.data() }, 77.25, collect); + expectEquals ((int) delivered.size(), 4); + expect (! delivered.empty() && delivered.back().message.isMidiClock()); + expectEquals (lastTime(), 77.25); + } + beginTest ("UMP SysEx7 messages interspersed with utility messages convert to bytestream"); { const auto sysEx = createRandomSysEx (random, 100); ``` -- Julius O. Smith III (CCRMA, Stanford / moForte) ---
**Author:** ![reuk](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.juce.com/reuk/32/21494_2.png) [@reuk](https://forum.juce.com/u/reuk)\ **Post date:** [August 25, 2026, 9:21am UTC](https://forum.juce.com/t/bug-patch-ump-bytestream-translator-delivers-a-single-packet-sysex7-with-a-zero-or-stale-timestamp-8-0-12-develop-9-0-1/69351/2 "2026-08-25T09:21:15Z")
Thanks for the report, that’s fixed here: >