diff --git a/db/upgrade/mod.rs b/db/upgrade/mod.rs
index 22cd8b7..f6ca38a 100644
--- a/db/upgrade/mod.rs
+++ b/db/upgrade/mod.rs
@@ -230,19 +230,31 @@ mod tests {
             insert into video_sample_entry (id, sha1, width, height, data)
                 values (3, X'0000000000000000000000000000000000000002', 704, 480, ?);
         "#, params![GOOD_ANAMORPHIC_VIDEO_SAMPLE_ENTRY])?;
+        upgraded.execute(r#"
+            insert into video_sample_entry (id, sha1, width, height, data)
+                values (4, X'0000000000000000000000000000000000000003', 704, 480, ?);
+        "#, params![GOOD_ANAMORPHIC_VIDEO_SAMPLE_ENTRY])?;
         upgraded.execute_batch(r#"
             insert into recording (id, camera_id, sample_file_bytes, start_time_90k, duration_90k,
                                    local_time_delta_90k, video_samples, video_sync_samples,
                                    video_sample_entry_id, sample_file_uuid, sample_file_sha1,
                                    video_index)
                            values (1, 1, 42, 140063580000000, 90000, 0, 1, 1, 1,
-                                   X'E69D45E8CBA64DC1BA2ECB1585983A10', zeroblob(20), X'00');
+                                   X'E69D45E8CBA64DC1BA2ECB1585983A10', zeroblob(20), X'00'),
+                                  (2, 1, 42, 140063580090000, 90000, 0, 1, 1, 2,
+                                   X'94DE8484FF874A5295D488C8038A0312', zeroblob(20), X'00'),
+                                  (3, 1, 42, 140063580180000, 90000, 0, 1, 1, 3,
+                                   X'C94D4D0B533746059CD40B29039E641E', zeroblob(20), X'00');
             insert into reserved_sample_files values (X'51EF700C933E4197AAE4EE8161E94221', 0),
                                                      (X'E69D45E8CBA64DC1BA2ECB1585983A10', 1);
         "#)?;
         let rec1 = tmpdir.path().join("e69d45e8-cba6-4dc1-ba2e-cb1585983a10");
+        let rec2 = tmpdir.path().join("94de8484-ff87-4a52-95d4-88c8038a0312");
+        let rec3 = tmpdir.path().join("c94d4d0b-5337-4605-9cd4-0b29039e641e");
         let garbage = tmpdir.path().join("51ef700c-933e-4197-aae4-ee8161e94221");
         std::fs::File::create(&rec1)?;
+        std::fs::File::create(&rec2)?;
+        std::fs::File::create(&rec3)?;
         std::fs::File::create(&garbage)?;
 
         for (ver, fresh_sql) in &[(1, Some(include_str!("v1.sql"))),
@@ -287,6 +299,9 @@ mod tests {
                 assert_eq!(pasp_by_id.get(&1), Some(&(1, 1)));
                 assert_eq!(pasp_by_id.get(&2), Some(&(4, 3)));
                 assert_eq!(pasp_by_id.get(&3), Some(&(40, 33)));
+
+                // No recording references this video_sample_entry, so it gets dropped on upgrade.
+                assert_eq!(pasp_by_id.get(&4), None);
             }
         }
 
diff --git a/db/upgrade/v5_to_v6.rs b/db/upgrade/v5_to_v6.rs
index fcab056..7dfef9a 100644
--- a/db/upgrade/v5_to_v6.rs
+++ b/db/upgrade/v5_to_v6.rs
@@ -31,7 +31,7 @@
 /// Upgrades a version 4 schema to a version 5 schema.
 
 use byteorder::{BigEndian, ByteOrder, WriteBytesExt};
-use failure::{Error, bail, format_err};
+use failure::{Error, ResultExt, bail, format_err};
 use h264_reader::avcc::AvcDecoderConfigurationRecord;
 use rusqlite::{named_params, params};
 use std::convert::{TryFrom, TryInto};
@@ -93,6 +93,10 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
                                 values (:id, :width, :height, :rfc6381_codec, :data,
                                         :pasp_h_spacing, :pasp_v_spacing)
     "#)?;
+
+    // Only insert still-referenced video sample entries. I've had problems with
+    // no-longer-referenced ones (perhaps from some ancient, buggy version of Moonfire NVR) for
+    // which avcc.create_context(()) fails.
     let mut stmt = tx.prepare(r#"
         select
           id,
@@ -101,7 +105,15 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
           rfc6381_codec,
           data
         from
-          old_video_sample_entry
+          old_video_sample_entry v
+        where
+          exists (
+            select
+              'x'
+            from
+              recording r
+            where
+              r.video_sample_entry_id = v.id)
     "#)?;
     let mut rows = stmt.query(params![])?;
     while let Some(row) = rows.next()? {
@@ -115,9 +127,10 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
             bail!("Multiple SPSs!");
         }
         let ctx = avcc.create_context(())
-            .map_err(|e| format_err!("Can't load SPS+PPS: {:?}", e))?;
+            .map_err(|e| format_err!("Can't load SPS+PPS for video_sample_entry_id {}: {:?}",
+                                     id, e))?;
         let sps = ctx.sps_by_id(h264_reader::nal::pps::ParamSetId::from_u32(0).unwrap())
-            .ok_or_else(|| format_err!("No SPS 0"))?;
+            .ok_or_else(|| format_err!("No SPS 0 for video_sample_entry_id {}", id))?;
         let pasp = sps.vui_parameters.as_ref()
                                      .and_then(|v| v.aspect_ratio_info.as_ref())
                                      .and_then(|a| a.clone().get())
@@ -257,8 +270,8 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
             ":video_samples": video_samples,
             ":video_sync_samples": video_sync_samples,
             ":video_sample_entry_id": video_sample_entry_id,
-        })?;
-        cum_duration_90k += duration_90k;
+        }).with_context(|_| format!("Unable to insert composite_id {}", composite_id))?;
+        cum_duration_90k += i64::from(duration_90k);
         cum_runs += if run_offset == 0 { 1 } else { 0 };
     }
     tx.execute_batch(r#"