[FFmpeg-devel] [PATCH 2/3] lavf/mkvtimestamp_v2: review implementation to match mkvextract behavior

[Stefano Sabatini]

Harmonize internal implementation with the mkvextract behavior:
- print PTS in place of DTS values
- ignore NOPTS values
- sort PTS values
---
 libavformat/mkvtimestamp_v2.c | 69 +++++++++++++++++++++++++++++++++--
 1 file changed, 65 insertions(+), 4 deletions(-)

diff --git a/libavformat/mkvtimestamp_v2.c b/libavformat/mkvtimestamp_v2.c
index 1eb2daf10a..c6446ed489 100644
--- a/libavformat/mkvtimestamp_v2.c
+++ b/libavformat/mkvtimestamp_v2.c
@@ -22,30 +22,91 @@
 #include "avformat.h"
 #include "internal.h"
 #include "mux.h"
+#include "libavutil/qsort.h"
+
+#define PTSS_MAX_SIZE 128
+#define PTSS_HALF_SIZE (PTSS_MAX_SIZE >> 1)
+
+struct MkvTimestampContext {
+    int64_t ptss[PTSS_MAX_SIZE];
+    size_t ptss_size;
+};
 
 static int write_header(AVFormatContext *s)
 {
-    static const char *header = "# timecode format v2\n";
+    static const char *header = "# timestamp format v2\n";
     avio_write(s->pb, header, strlen(header));
     avpriv_set_pts_info(s->streams[0], 64, 1, 1000);
+
     return 0;
 }
 
+static int cmp_int64(const void *p1, const void *p2)
+{
+    int64_t left  = *(const int64_t *)p1;
+    int64_t right = *(const int64_t *)p2;
+    return FFDIFFSIGN(left, right);
+}
+
 static int write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     char buf[256];
+    int i;
+    struct MkvTimestampContext *m = s->priv_data;
+
     if (pkt->stream_index)
         av_log(s, AV_LOG_WARNING, "More than one stream unsupported\n");
-    snprintf(buf, sizeof(buf), "%" PRId64 "\n", pkt->dts);
-    avio_write(s->pb, buf, strlen(buf));
+
+    if (pkt->pts == AV_NOPTS_VALUE) {
+        av_log(s, AV_LOG_WARNING, "Found PTS with no value, ignored\n");
+        return 0;
+    }
+
+    if (m->ptss_size > PTSS_MAX_SIZE) {
+        // sort all PTSs
+        AV_QSORT(m->ptss, PTSS_MAX_SIZE, int64_t, cmp_int64);
+
+        // write only the first half and copy the second half to the
+        // beginning of the array
+        for (i = 0; i < PTSS_HALF_SIZE; i++) {
+            snprintf(buf, sizeof(buf), "%" PRId64 "\n", m->ptss[i]);
+            avio_write(s->pb, buf, strlen(buf));
+            m->ptss[i] = m->ptss[i + PTSS_HALF_SIZE];
+        }
+
+        m->ptss_size = PTSS_HALF_SIZE;
+    } else {
+        m->ptss[m->ptss_size++] = pkt->pts;
+    }
+
+    return 0;
+}
+
+static int write_trailer(struct AVFormatContext *s)
+{
+    struct MkvTimestampContext *m = s->priv_data;
+    char buf[256];
+    int i;
+
+    // sort all PTSs
+    AV_QSORT(m->ptss, m->ptss_size, int64_t, cmp_int64);
+
+    /* flush remaining timestamps */
+    for (i = 0; i < m->ptss_size; i++) {
+        snprintf(buf, sizeof(buf), "%" PRId64 "\n", m->ptss[i]);
+        avio_write(s->pb, buf, strlen(buf));
+    }
+
     return 0;
 }
 
 const FFOutputFormat ff_mkvtimestamp_v2_muxer = {
     .p.name        = "mkvtimestamp_v2",
-    .p.long_name   = NULL_IF_CONFIG_SMALL("mkvtoolnix v2 timecode format"),
+    .p.long_name   = NULL_IF_CONFIG_SMALL("mkvtoolnix v2 timestamp format"),
     .p.audio_codec = AV_CODEC_ID_NONE,
     .p.video_codec = AV_CODEC_ID_RAWVIDEO,
     .write_header = write_header,
     .write_packet = write_packet,
+    .write_trailer = write_trailer,
+    .priv_data_size = sizeof(struct MkvTimestampContext),
 };
-- 
2.34.1