segment: Add an option for omitting the first header and final trailer

This allows writing totally bare segments, without any header/trailer
included anywhere.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/segment.c

@@ -41,6 +41,7 @@ typedef struct {
     int  size;             /**< Set by a private option. */
     int  wrap;             /**< Set by a private option. */
     int  individual_header_trailer; /**< Set by a private option. */
+    int  write_header_trailer; /**< Set by a private option. */
     int64_t offset_time;
     int64_t recording_time;
     int has_video;
@@ -119,6 +120,26 @@ static int segment_end(AVFormatContext *oc, int write_trailer)
     return ret;
 }
 
+static int open_null_ctx(AVIOContext **ctx)
+{
+    int buf_size = 32768;
+    uint8_t *buf = av_malloc(buf_size);
+    if (!buf)
+        return AVERROR(ENOMEM);
+    *ctx = avio_alloc_context(buf, buf_size, AVIO_FLAG_WRITE, NULL, NULL, NULL, NULL);
+    if (!*ctx) {
+        av_free(buf);
+        return AVERROR(ENOMEM);
+    }
+    return 0;
+}
+
+static void close_null_ctx(AVIOContext *pb)
+{
+    av_free(pb->buffer);
+    av_free(pb);
+}
+
 static int seg_write_header(AVFormatContext *s)
 {
     SegmentContext *seg = s->priv_data;
@@ -128,6 +149,8 @@ static int seg_write_header(AVFormatContext *s)
     seg->number = 0;
     seg->offset_time = 0;
     seg->recording_time = seg->time * 1000000;
+    if (!seg->write_header_trailer)
+        seg->individual_header_trailer = 0;
 
     if (seg->list)
         if ((ret = avio_open2(&seg->pb, seg->list, AVIO_FLAG_WRITE,
@@ -166,15 +189,27 @@ static int seg_write_header(AVFormatContext *s)
         goto fail;
     }
 
-    if ((ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
-                          &s->interrupt_callback, NULL)) < 0)
-        goto fail;
+    if (seg->write_header_trailer) {
+        if ((ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
+                              &s->interrupt_callback, NULL)) < 0)
+            goto fail;
+    } else {
+        if ((ret = open_null_ctx(&oc->pb)) < 0)
+            goto fail;
+    }
 
     if ((ret = avformat_write_header(oc, NULL)) < 0) {
         avio_close(oc->pb);
         goto fail;
     }
 
+    if (!seg->write_header_trailer) {
+        close_null_ctx(oc->pb);
+        if ((ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
+                              &s->interrupt_callback, NULL)) < 0)
+            goto fail;
+    }
+
     if (seg->list) {
         avio_printf(seg->pb, "%s\n", oc->filename);
         avio_flush(seg->pb);
@@ -244,7 +279,15 @@ static int seg_write_trailer(struct AVFormatContext *s)
 {
     SegmentContext *seg = s->priv_data;
     AVFormatContext *oc = seg->avf;
-    int ret = segment_end(oc);
+    int ret;
+    if (!seg->write_header_trailer) {
+        ret = segment_end(oc, 0);
+        open_null_ctx(&oc->pb);
+        av_write_trailer(oc);
+        close_null_ctx(oc->pb);
+    } else {
+        ret = segment_end(oc, 1);
+    }
     if (seg->list)
         avio_close(seg->pb);
     avformat_free_context(oc);
@@ -260,6 +303,7 @@ static const AVOption options[] = {
     { "segment_list_size", "maximum number of playlist entries",      OFFSET(size),    AV_OPT_TYPE_INT,    {.i64 = 5},     0, INT_MAX, E },
     { "segment_wrap",      "number after which the index wraps",      OFFSET(wrap),    AV_OPT_TYPE_INT,    {.i64 = 0},     0, INT_MAX, E },
     { "individual_header_trailer", "write header/trailer to each segment", OFFSET(individual_header_trailer), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, E },
+    { "write_header_trailer", "write a header to the first segment and a trailer to the last one", OFFSET(write_header_trailer), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, E },
     { NULL },
 };