diff --git a/media/libmediametrics/include/media/MediaMetricsItem.h b/media/libmediametrics/include/media/MediaMetricsItem.h
index 08720f1..591e714 100644
--- a/media/libmediametrics/include/media/MediaMetricsItem.h
+++ b/media/libmediametrics/include/media/MediaMetricsItem.h
@@ -208,11 +208,11 @@
 
 template<size_t N>
 static inline bool startsWith(const std::string &s, const char (&comp)[N]) {
-    return !strncmp(s.c_str(), comp, N - 1);
+    return !strncmp(s.c_str(), comp, N - 1); // last char is null termination
 }
 
 static inline bool startsWith(const std::string& s, const std::string& comp) {
-    return !strncmp(s.c_str(), comp.c_str(), comp.size() - 1);
+    return !strncmp(s.c_str(), comp.c_str(), comp.size());
 }
 
 /**
diff --git a/services/mediametrics/AnalyticsState.h b/services/mediametrics/AnalyticsState.h
index 290ed21..e8fedcf 100644
--- a/services/mediametrics/AnalyticsState.h
+++ b/services/mediametrics/AnalyticsState.h
@@ -84,8 +84,11 @@
      * delivered.
      *
      * \param lines the maximum number of lines in the string returned.
+     * \param sinceNs the nanoseconds since Unix epoch to start dump (0 shows all)
+     * \param prefix the desired key prefix to match (nullptr shows all)
      */
-    std::pair<std::string, int32_t> dump(int32_t lines = INT32_MAX) const {
+    std::pair<std::string, int32_t> dump(
+            int32_t lines = INT32_MAX, int64_t sinceNs = 0, const char *prefix = nullptr) const {
         std::stringstream ss;
         int32_t ll = lines;
 
@@ -94,8 +97,8 @@
             --ll;
         }
         if (ll > 0) {
-            auto [s, l] = mTransactionLog.dump(ll);
-            ss << s;
+            auto [s, l] = mTransactionLog.dump(ll, sinceNs, prefix);
+            ss << std::move(s);
             ll -= l;
         }
         if (ll > 0) {
@@ -103,8 +106,8 @@
             --ll;
         }
         if (ll > 0) {
-            auto [s, l] = mTimeMachine.dump(ll);
-            ss << s;
+            auto [s, l] = mTimeMachine.dump(ll, sinceNs, prefix);
+            ss << std::move(s);
             ll -= l;
         }
         return { ss.str(), lines - ll };
diff --git a/services/mediametrics/AudioAnalytics.cpp b/services/mediametrics/AudioAnalytics.cpp
index 126e501..f80516e 100644
--- a/services/mediametrics/AudioAnalytics.cpp
+++ b/services/mediametrics/AudioAnalytics.cpp
@@ -107,14 +107,15 @@
     return NO_ERROR;
 }
 
-std::pair<std::string, int32_t> AudioAnalytics::dump(int32_t lines) const
+std::pair<std::string, int32_t> AudioAnalytics::dump(
+        int32_t lines, int64_t sinceNs, const char *prefix) const
 {
     std::stringstream ss;
     int32_t ll = lines;
 
     if (ll > 0) {
-        auto [s, l] = mAnalyticsState->dump(ll);
-        ss << s;
+        auto [s, l] = mAnalyticsState->dump(ll, sinceNs, prefix);
+        ss << std::move(s);
         ll -= l;
     }
     if (ll > 0) {
@@ -122,8 +123,8 @@
         --ll;
     }
     if (ll > 0) {
-        auto [s, l] = mPreviousAnalyticsState->dump(ll);
-        ss << s;
+        auto [s, l] = mPreviousAnalyticsState->dump(ll, sinceNs, prefix);
+        ss << std::move(s);
         ll -= l;
     }
     return { ss.str(), lines - ll };
diff --git a/services/mediametrics/AudioAnalytics.h b/services/mediametrics/AudioAnalytics.h
index 4a42e22..ba4c3f2 100644
--- a/services/mediametrics/AudioAnalytics.h
+++ b/services/mediametrics/AudioAnalytics.h
@@ -60,8 +60,17 @@
      * delivered.
      *
      * \param lines the maximum number of lines in the string returned.
+     * \param sinceNs the nanoseconds since Unix epoch to start dump (0 shows all)
+     * \param prefix the desired key prefix to match (nullptr shows all)
      */
-    std::pair<std::string, int32_t> dump(int32_t lines = INT32_MAX) const;
+    std::pair<std::string, int32_t> dump(
+            int32_t lines = INT32_MAX, int64_t sinceNs = 0, const char *prefix = nullptr) const;
+
+    void clear() {
+        // underlying state is locked.
+        mPreviousAnalyticsState->clear();
+        mAnalyticsState->clear();
+    }
 
 private:
 
diff --git a/services/mediametrics/MediaMetricsService.cpp b/services/mediametrics/MediaMetricsService.cpp
index d76bc2c..b9703ba 100644
--- a/services/mediametrics/MediaMetricsService.cpp
+++ b/services/mediametrics/MediaMetricsService.cpp
@@ -207,69 +207,66 @@
         return NO_ERROR;
     }
 
+    static const String16 allOption("--all");
+    static const String16 clearOption("--clear");
     static const String16 heapOption("--heap");
+    static const String16 helpOption("--help");
+    static const String16 prefixOption("--prefix");
+    static const String16 sinceOption("--since");
     static const String16 unreachableOption("--unreachable");
+
+    bool all = false;
+    bool clear = false;
     bool heap = false;
     bool unreachable = false;
+    int64_t sinceNs = 0;
+    std::string prefix;
 
-    const String16 protoOption("--proto");
-    const String16 clearOption("--clear");
-    bool clear = false;
-    const String16 sinceOption("--since");
-    nsecs_t ts_since = 0;
-    const String16 helpOption("--help");
-    const String16 onlyOption("--only");
-    std::string only;
-    const int n = args.size();
-    for (int i = 0; i < n; i++) {
-        if (args[i] == clearOption) {
+    const size_t n = args.size();
+    for (size_t i = 0; i < n; i++) {
+        if (args[i] == allOption) {
+            all = true;
+        } else if (args[i] == clearOption) {
             clear = true;
         } else if (args[i] == heapOption) {
             heap = true;
-        } else if (args[i] == protoOption) {
-            i++;
-            if (i < n) {
-                // ignore
-            } else {
-                result.append("missing value for -proto\n\n");
-            }
-        } else if (args[i] == sinceOption) {
-            i++;
-            if (i < n) {
-                String8 value(args[i]);
-                char *endp;
-                const char *p = value.string();
-                ts_since = strtoll(p, &endp, 10);
-                if (endp == p || *endp != '\0') {
-                    ts_since = 0;
-                }
-            } else {
-                ts_since = 0;
-            }
-            // command line is milliseconds; internal units are nano-seconds
-            ts_since *= NANOS_PER_MILLISECOND;
-        } else if (args[i] == onlyOption) {
-            i++;
-            if (i < n) {
-                String8 value(args[i]);
-                only = value.string();
-            }
         } else if (args[i] == helpOption) {
             // TODO: consider function area dumping.
             // dumpsys media.metrics audiotrack,codec
             // or dumpsys media.metrics audiotrack codec
 
             result.append("Recognized parameters:\n");
-            result.append("--heap        heap usage (top 100)\n");
-            result.append("--help        this help message\n");
-            result.append("--proto #     dump using protocol #");
-            result.append("--clear       clears out saved records\n");
-            result.append("--only X      process records for component X\n");
-            result.append("--since X     include records since X\n");
-            result.append("             (X is milliseconds since the UNIX epoch)\n");
-            result.append("--unreachable unreachable memory (leaks)\n");
+            result.append("--all         show all records\n");
+            result.append("--clear       clear out saved records\n");
+            result.append("--heap        show heap usage (top 100)\n");
+            result.append("--help        display help\n");
+            result.append("--prefix X    process records for component X\n");
+            result.append("--since X     X < 0: records from -X seconds in the past\n");
+            result.append("              X = 0: ignore\n");
+            result.append("              X > 0: records from X seconds since Unix epoch\n");
+            result.append("--unreachable show unreachable memory (leaks)\n");
             write(fd, result.string(), result.size());
             return NO_ERROR;
+        } else if (args[i] == prefixOption) {
+            ++i;
+            if (i < n) {
+                prefix = String8(args[i]).string();
+            }
+        } else if (args[i] == sinceOption) {
+            ++i;
+            if (i < n) {
+                String8 value(args[i]);
+                char *endp;
+                const char *p = value.string();
+                long long sec = strtoll(p, &endp, 10);
+                if (endp == p || *endp != '\0' || sec == 0) {
+                    sinceNs = 0;
+                } else if (sec < 0) {
+                    sinceNs = systemTime(SYSTEM_TIME_REALTIME) + sec * NANOS_PER_SECOND;
+                } else {
+                    sinceNs = sec * NANOS_PER_SECOND;
+                }
+            }
         } else if (args[i] == unreachableOption) {
             unreachable = true;
         }
@@ -278,21 +275,23 @@
     {
         std::lock_guard _l(mLock);
 
-        result.appendFormat("Dump of the %s process:\n", kServiceName);
-        dumpHeaders_l(result, ts_since);
-        dumpRecent_l(result, ts_since, only.c_str());
-
         if (clear) {
             mItemsDiscarded += mItems.size();
             mItems.clear();
-            // shall we clear the summary data too?
-        }
-        // TODO: maybe consider a better way of dumping audio analytics info.
-        constexpr int32_t linesToDump = 1000;
-        auto [ dumpString, lines ] = mAudioAnalytics.dump(linesToDump);
-        result.append(dumpString.c_str());
-        if (lines == linesToDump) {
-            result.append("-- some lines may be truncated --\n");
+            mAudioAnalytics.clear();
+        } else {
+            result.appendFormat("Dump of the %s process:\n", kServiceName);
+            const char *prefixptr = prefix.size() > 0 ? prefix.c_str() : nullptr;
+            dumpHeaders_l(result, sinceNs, prefixptr);
+            dumpQueue_l(result, sinceNs, prefixptr);
+
+            // TODO: maybe consider a better way of dumping audio analytics info.
+            const int32_t linesToDump = all ? INT32_MAX : 1000;
+            auto [ dumpString, lines ] = mAudioAnalytics.dump(linesToDump, sinceNs, prefixptr);
+            result.append(dumpString.c_str());
+            if (lines == linesToDump) {
+                result.append("-- some lines may be truncated --\n");
+            }
         }
     }
     write(fd, result.string(), result.size());
@@ -313,7 +312,7 @@
 }
 
 // dump headers
-void MediaMetricsService::dumpHeaders_l(String8 &result, nsecs_t ts_since)
+void MediaMetricsService::dumpHeaders_l(String8 &result, int64_t sinceNs, const char* prefix)
 {
     if (mediametrics::Item::isEnabled()) {
         result.append("Metrics gathering: enabled\n");
@@ -327,54 +326,36 @@
             "Records Discarded: %lld (by Count: %lld by Expiration: %lld)\n",
             (long long)mItemsDiscarded, (long long)mItemsDiscardedCount,
             (long long)mItemsDiscardedExpire);
-    if (ts_since != 0) {
+    if (prefix != nullptr) {
+        result.appendFormat("Restricting to prefix %s", prefix);
+    }
+    if (sinceNs != 0) {
         result.appendFormat(
             "Emitting Queue entries more recent than: %lld\n",
-            (long long)ts_since);
+            (long long)sinceNs);
     }
 }
 
-void MediaMetricsService::dumpRecent_l(
-        String8 &result, nsecs_t ts_since, const char * only)
+// TODO: should prefix be a set<string>?
+void MediaMetricsService::dumpQueue_l(String8 &result, int64_t sinceNs, const char* prefix)
 {
-    if (only != nullptr && *only == '\0') {
-        only = nullptr;
-    }
-    result.append("\nFinalized Metrics (oldest first):\n");
-    dumpQueue_l(result, ts_since, only);
-
-    // show who is connected and injecting records?
-    // talk about # records fed to the 'readers'
-    // talk about # records we discarded, perhaps "discarded w/o reading" too
-}
-
-void MediaMetricsService::dumpQueue_l(String8 &result) {
-    dumpQueue_l(result, (nsecs_t) 0, nullptr /* only */);
-}
-
-void MediaMetricsService::dumpQueue_l(
-        String8 &result, nsecs_t ts_since, const char * only) {
-    int slot = 0;
-
     if (mItems.empty()) {
         result.append("empty\n");
-    } else {
-        for (const auto &item : mItems) {
-            nsecs_t when = item->getTimestamp();
-            if (when < ts_since) {
-                continue;
-            }
-            // TODO: Only should be a set<string>
-            if (only != nullptr &&
-                    item->getKey() /* std::string */ != only) {
-                ALOGV("%s: omit '%s', it's not '%s'",
-                        __func__, item->getKey().c_str(), only);
-                continue;
-            }
-            result.appendFormat("%5d: %s\n",
-                   slot, item->toString().c_str());
-            slot++;
+        return;
+    }
+
+    int slot = 0;
+    for (const auto &item : mItems) {         // TODO: consider std::lower_bound() on mItems
+        if (item->getTimestamp() < sinceNs) { // sinceNs == 0 means all items shown
+            continue;
         }
+        if (prefix != nullptr && !startsWith(item->getKey(), prefix)) {
+            ALOGV("%s: omit '%s', it's not '%s'",
+                    __func__, item->getKey().c_str(), prefix);
+            continue;
+        }
+        result.appendFormat("%5d: %s\n", slot, item->toString().c_str());
+        slot++;
     }
 }
 
diff --git a/services/mediametrics/MediaMetricsService.h b/services/mediametrics/MediaMetricsService.h
index 935bee2..a93f7fb 100644
--- a/services/mediametrics/MediaMetricsService.h
+++ b/services/mediametrics/MediaMetricsService.h
@@ -85,11 +85,8 @@
     bool expirations_l(const std::shared_ptr<const mediametrics::Item>& item);
 
     // support for generating output
-    void dumpQueue_l(String8 &result);
-    void dumpQueue_l(String8 &result, nsecs_t, const char *only);
-    void dumpHeaders_l(String8 &result, nsecs_t ts_since);
-    void dumpSummaries_l(String8 &result, nsecs_t ts_since, const char * only);
-    void dumpRecent_l(String8 &result, nsecs_t ts_since, const char * only);
+    void dumpQueue_l(String8 &result, int64_t sinceNs, const char* prefix);
+    void dumpHeaders_l(String8 &result, int64_t sinceNs, const char* prefix);
 
     // The following variables accessed without mLock
 
diff --git a/services/mediametrics/TimeMachine.h b/services/mediametrics/TimeMachine.h
index a4c3693..75819ba 100644
--- a/services/mediametrics/TimeMachine.h
+++ b/services/mediametrics/TimeMachine.h
@@ -149,8 +149,11 @@
             int32_t ll = lines;
             for (auto& tsPair : mPropertyMap) {
                 if (ll <= 0) break;
-                ss << dump(mKey, tsPair, time);
-                --ll;
+                std::string s = dump(mKey, tsPair, time);
+                if (s.size() > 0) {
+                    --ll;
+                    ss << std::move(s);
+                }
             }
             return { ss.str(), lines - ll };
         }
@@ -165,7 +168,7 @@
             const auto timeSequence = tsPair.second;
             auto eptr = timeSequence.lower_bound(time);
             if (eptr == timeSequence.end()) {
-                return tsPair.first + "={};\n";
+                return {}; // don't dump anything. tsPair.first + "={};\n";
             }
             std::stringstream ss;
             ss << key << "." << tsPair.first << "={";
@@ -407,25 +410,23 @@
      *
      * \param lines the maximum number of lines in the string returned.
      * \param key selects only that key.
-     * \param time to start the dump from.
+     * \param sinceNs the nanoseconds since Unix epoch to start dump (0 shows all)
+     * \param prefix the desired key prefix to match (nullptr shows all)
      */
     std::pair<std::string, int32_t> dump(
-            int32_t lines = INT32_MAX, const std::string &key = {}, int64_t time = 0) const {
+            int32_t lines = INT32_MAX, int64_t sinceNs = 0, const char *prefix = nullptr) const {
         std::lock_guard lock(mLock);
-        if (!key.empty()) {  // use std::regex
-            const auto it = mHistory.find(key);
-            if (it == mHistory.end()) return {};
-            std::lock_guard lock(getLockForKey(it->first));
-            return it->second->dump(lines, time);
-        }
-
         std::stringstream ss;
         int32_t ll = lines;
-        for (const auto &[lkey, lhist] : mHistory) {
-            std::lock_guard lock(getLockForKey(lkey));
-            if (lines <= 0) break;
-            auto [s, l] = lhist->dump(ll, time);
-            ss << s;
+
+        for (auto it = prefix != nullptr ? mHistory.lower_bound(prefix) : mHistory.begin();
+                it != mHistory.end();
+                ++it) {
+            if (ll <= 0) break;
+            if (prefix != nullptr && !startsWith(it->first, prefix)) break;
+            std::lock_guard lock(getLockForKey(it->first));
+            auto [s, l] = it->second->dump(ll, sinceNs);
+            ss << std::move(s);
             ll -= l;
         }
         return { ss.str(), lines - ll };
diff --git a/services/mediametrics/TransactionLog.h b/services/mediametrics/TransactionLog.h
index 190a99e..2359eec 100644
--- a/services/mediametrics/TransactionLog.h
+++ b/services/mediametrics/TransactionLog.h
@@ -127,8 +127,11 @@
      * for subsequent line limiting.
      *
      * \param lines the maximum number of lines in the string returned.
+     * \param sinceNs the nanoseconds since Unix epoch to start dump (0 shows all)
+     * \param prefix the desired key prefix to match (nullptr shows all)
      */
-    std::pair<std::string, int32_t> dump(int32_t lines) const {
+    std::pair<std::string, int32_t> dump(
+            int32_t lines, int64_t sinceNs, const char *prefix = nullptr) const {
         std::stringstream ss;
         int32_t ll = lines;
         std::lock_guard lock(mLock);
@@ -138,26 +141,25 @@
             ss << "Consolidated:\n";
             --ll;
         }
-        for (const auto &log : mLog) {
-            if (ll <= 0) break;
-            ss << "  " << log.second->toString() << "\n";
-            --ll;
-        }
+        auto [s, l] = dumpMapTimeItem(mLog, ll, sinceNs, prefix);
+        ss << std::move(s);
+        ll -= l;
 
         // Grouped by item key (category)
         if (ll > 0) {
             ss << "Categorized:\n";
             --ll;
         }
-        for (const auto &itemMap : mItemMap) {
+
+        for (auto it = prefix != nullptr ? mItemMap.lower_bound(prefix) : mItemMap.begin();
+                it != mItemMap.end();
+                ++it) {
             if (ll <= 0) break;
-            ss << " " << itemMap.first << "\n";
-            --ll;
-            for (const auto &item : itemMap.second) {
-                if (ll <= 0) break;
-                ss << "  " << item.second->toString() << "\n";
-                --ll;
-            }
+            if (prefix != nullptr && !startsWith(it->first, prefix)) break;
+            auto [s, l] = dumpMapTimeItem(it->second, ll - 1, sinceNs, prefix);
+            if (l == 0) continue; // don't show empty groups (due to sinceNs).
+            ss << " " << it->first << "\n" << std::move(s);
+            ll -= l + 1;
         }
         return { ss.str(), lines - ll };
     }
@@ -184,6 +186,24 @@
     using MapTimeItem =
             std::multimap<int64_t /* time */, std::shared_ptr<const mediametrics::Item>>;
 
+    static std::pair<std::string, int32_t> dumpMapTimeItem(
+            const MapTimeItem& mapTimeItem,
+            int32_t lines, int64_t sinceNs = 0, const char *prefix = nullptr) {
+        std::stringstream ss;
+        int32_t ll = lines;
+        // Note: for our data, mapTimeItem.lower_bound(0) == mapTimeItem.begin().
+        for (auto it = mapTimeItem.lower_bound(sinceNs);
+                it != mapTimeItem.end(); ++it) {
+            if (ll <= 0) break;
+            if (prefix != nullptr && !startsWith(it->second->getKey(), prefix)) {
+                continue;
+            }
+            ss << "  " << it->second->toString() << "\n";
+            --ll;
+        }
+        return { ss.str(), lines - ll };
+    }
+
     // GUARDED_BY mLock
     /**
      * Garbage collects if the TimeMachine size exceeds the high water mark.