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avformat/segment: Various segment muxer improvements #96

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79b4f63
avformat/segment: Add segment_write_temp option
softworkz Jun 13, 2025
10b1c22
avformat/segment: Add segment_limit option
softworkz Jun 13, 2025
a855134
avformat/segment: Remove non-negative constraint from segment_time_delta
softworkz Sep 2, 2019
33139f2
avformat/segment: Don't allow negative segment duration
softworkz Sep 2, 2019
64451d0
avformat/segment: Fix typo
softworkz Jun 13, 2025
cb32675
avformat/segment: Indent and whitespace fixes
softworkz Jun 13, 2025
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12 changes: 12 additions & 0 deletions doc/muxers.texi
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Original file line number Diff line number Diff line change
Expand Up @@ -3505,6 +3505,18 @@ argument must be a time duration specification, and defaults to 0.
If enabled, write an empty segment if there are no packets during the period a
segment would usually span. Otherwise, the segment will be filled with the next
packet written. Defaults to @code{0}.

@item segment_write_temp @var{1|0}
Write segments to files with a .tmp extension. Each file is renamed to its
actual name on completion. This can help to prevent segment files from
being accessed before they are complete. Disabled by default (@code{0}).

@item segment_limit @var{number}
Stops after the specified number of segments has been generated.
This can be helpful to fill gaps in a range of already generated segments,
which is difficult to achieve otherwise as it would either cause the last
segment to be incomplete or to overwrite an existing segment with a partial
data. Default is @code{0} - no limit.
@end table

Make sure to require a closed GOP when encoding and to set the GOP
Expand Down
95 changes: 64 additions & 31 deletions libavformat/segment.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@

/**
* @file generic segmenter
* M3U8 specification can be find here:
* M3U8 specification can be found here:
* @url{http://tools.ietf.org/id/draft-pantos-http-live-streaming}
*/

Expand Down Expand Up @@ -121,6 +121,9 @@ typedef struct SegmentContext {
int break_non_keyframes;
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@ffmpeg-codebot ffmpeg-codebot bot Jun 14, 2025

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On the FFmpeg mailing list, Michael Niedermayer wrote (reply to this):


--===============8122640100284245730==
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On Sat, Jun 14, 2025 at 12:59:10AM +0000, softworkz wrote:
> From: softworkz <[email protected]>
>=20
> Signed-off-by: softworkz <[email protected]>
> ---
>  libavformat/segment.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

should be ok

thx

[...]
--=20
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored answer#1 FFmpeg bugs should be sent to our bugtracker. U=
ser
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.

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_______________________________________________
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https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
[email protected] with subject "unsubscribe".

--===============8122640100284245730==--

int write_empty;

int segment_limit; ///< max number of segments to create

int segment_write_temp; ///< write segments as temp files and rename on completion
int use_rename;
char temp_list_filename[1024];

Expand Down Expand Up @@ -174,7 +177,7 @@ static int segment_mux_init(AVFormatContext *s)
return AVERROR(ENOMEM);
opar = st->codecpar;
if (!oc->oformat->codec_tag ||
av_codec_get_id (oc->oformat->codec_tag, ipar->codec_tag) == opar->codec_id ||
av_codec_get_id(oc->oformat->codec_tag, ipar->codec_tag) == opar->codec_id ||
av_codec_get_tag(oc->oformat->codec_tag, ipar->codec_id) <= 0) {
opar->codec_tag = ipar->codec_tag;
} else {
Expand Down Expand Up @@ -226,6 +229,14 @@ static int set_segment_filename(AVFormatContext *s)
seg->entry_prefix ? seg->entry_prefix : "",
av_basename(oc->url));

// Write segment as a temp file and rename on completion
if(seg->segment_write_temp) {
char *temp_name = av_asprintf("%s%s", buf, ".tmp");
if (!temp_name)
return AVERROR(ENOMEM);
ff_format_set_url(oc, temp_name);
}

return 0;
}

Expand Down Expand Up @@ -328,17 +339,17 @@ static void segment_list_print_entry(AVIOContext *list_ioctx,
list_entry->end_time - list_entry->start_time, list_entry->filename);
break;
case LIST_TYPE_FFCONCAT:
{
char *buf;
if (av_escape(&buf, list_entry->filename, NULL, AV_ESCAPE_MODE_AUTO, AV_ESCAPE_FLAG_WHITESPACE) < 0) {
av_log(log_ctx, AV_LOG_WARNING,
"Error writing list entry '%s' in list file\n", list_entry->filename);
return;
{
char *buf;
if (av_escape(&buf, list_entry->filename, NULL, AV_ESCAPE_MODE_AUTO, AV_ESCAPE_FLAG_WHITESPACE) < 0) {
av_log(log_ctx, AV_LOG_WARNING,
"Error writing list entry '%s' in list file\n", list_entry->filename);
return;
}
avio_printf(list_ioctx, "file %s\n", buf);
av_free(buf);
break;
}
avio_printf(list_ioctx, "file %s\n", buf);
av_free(buf);
break;
}
default:
av_assert0(!"Invalid list type");
}
Expand All @@ -356,6 +367,9 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
int i;
int err;

if (seg->segment_limit && seg->segment_count >= seg->segment_limit)
return 0;

if (!oc || !oc->pb)
return AVERROR(EINVAL);

Expand All @@ -372,7 +386,7 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
SegmentListEntry *entry = av_mallocz(sizeof(*entry));
if (!entry) {
ret = AVERROR(ENOMEM);
goto end;
goto fail;
}

/* append new element */
Expand All @@ -393,7 +407,7 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
}

if ((ret = segment_list_open(s)) < 0)
goto end;
goto fail;
for (entry = seg->segment_list_entries; entry; entry = entry->next)
segment_list_print_entry(seg->list_pb, seg->list_type, entry, s);
if (seg->list_type == LIST_TYPE_M3U8 && is_last)
Expand Down Expand Up @@ -443,14 +457,27 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
av_log(s, AV_LOG_WARNING, "Could not increment stream %d timecode, error occurred during timecode creation.\n", i);
continue;
}
st_tc.start += (int)((seg->cur_entry.end_time - seg->cur_entry.start_time) * av_q2d(st_rate)); // increment timecode
av_dict_set(&s->streams[i]->metadata, "timecode", av_timecode_make_string(&st_tc, st_buf, 0), 0);
st_tc.start += (int)((seg->cur_entry.end_time - seg->cur_entry.start_time) * av_q2d(st_rate)); // increment timecode
av_dict_set(&s->streams[i]->metadata, "timecode", av_timecode_make_string(&st_tc, st_buf, 0), 0);
}
}
}
}

end:
ff_format_io_close(oc, &oc->pb);

// Now rename the .tmp file to its actual name.
if (seg->segment_write_temp) {
char *final_filename = av_strndup(oc->url, strlen(oc->url) - 4);
if (!final_filename)
return AVERROR(ENOMEM);
ret = ff_rename(oc->url, final_filename, s);
av_free(final_filename);
}

return ret;

fail:
ff_format_io_close(oc, &oc->pb);

return ret;
Expand Down Expand Up @@ -723,8 +750,8 @@ static int seg_init(AVFormatContext *s)

if (seg->list) {
if (seg->list_type == LIST_TYPE_UNDEFINED) {
if (av_match_ext(seg->list, "csv" )) seg->list_type = LIST_TYPE_CSV;
else if (av_match_ext(seg->list, "ext" )) seg->list_type = LIST_TYPE_EXT;
if (av_match_ext(seg->list, "csv")) seg->list_type = LIST_TYPE_CSV;
else if (av_match_ext(seg->list, "ext")) seg->list_type = LIST_TYPE_EXT;
else if (av_match_ext(seg->list, "m3u8")) seg->list_type = LIST_TYPE_M3U8;
else if (av_match_ext(seg->list, "ffcat,ffconcat")) seg->list_type = LIST_TYPE_FFCONCAT;
else seg->list_type = LIST_TYPE_FLAT;
Expand Down Expand Up @@ -857,6 +884,9 @@ static int seg_write_packet(AVFormatContext *s, AVPacket *pkt)
int64_t usecs;
int64_t wrapped_val;

if (seg->segment_limit && seg->segment_count >= seg->segment_limit)
return 0;

if (!seg->avf || !seg->avf->pb)
return AVERROR(EINVAL);

Expand All @@ -875,11 +905,9 @@ static int seg_write_packet(AVFormatContext *s, AVPacket *pkt)

calc_times:
if (seg->times) {
end_pts = seg->segment_count < seg->nb_times ?
seg->times[seg->segment_count] : INT64_MAX;
end_pts = seg->segment_count < seg->nb_times ? seg->times[seg->segment_count] : INT64_MAX;
} else if (seg->frames) {
start_frame = seg->segment_count < seg->nb_frames ?
seg->frames[seg->segment_count] : INT_MAX;
start_frame = seg->segment_count < seg->nb_frames ? seg->frames[seg->segment_count] : INT_MAX;
} else {
if (seg->use_clocktime) {
int64_t avgt = av_gettime();
Expand Down Expand Up @@ -920,17 +948,20 @@ static int seg_write_packet(AVFormatContext *s, AVPacket *pkt)
(pkt->flags & AV_PKT_FLAG_KEY || seg->break_non_keyframes) &&
(seg->segment_frame_count > 0 || seg->write_empty) &&
(seg->cut_pending || seg->frame_count >= start_frame ||
(pkt->pts != AV_NOPTS_VALUE &&
pkt_pts_avtb - seg->cur_entry.start_pts >= seg->min_seg_duration &&
av_compare_ts(pkt->pts, st->time_base,
end_pts - seg->time_delta, AV_TIME_BASE_Q) >= 0))) {
(pkt->pts != AV_NOPTS_VALUE &&
pkt_pts_avtb - seg->cur_entry.start_pts >= seg->min_seg_duration &&
av_compare_ts(pkt->pts, st->time_base,
end_pts - seg->time_delta, AV_TIME_BASE_Q) >= 0))) {
/* sanitize end time in case last packet didn't have a defined duration */
if (seg->cur_entry.last_duration == 0)
seg->cur_entry.end_time = (double)pkt->pts * av_q2d(st->time_base);

if ((ret = segment_end(s, seg->individual_header_trailer, 0)) < 0)
goto fail;

if (seg->segment_limit && seg->segment_count >= seg->segment_limit)
return 0;

if ((ret = segment_start(s, seg->individual_header_trailer)) < 0)
goto fail;

Expand Down Expand Up @@ -1023,8 +1054,8 @@ static int seg_check_bitstream(AVFormatContext *s, AVStream *st,
if (ret == 1) {
FFStream *const sti = ffstream(st);
FFStream *const osti = ffstream(ost);
sti->bsfc = osti->bsfc;
osti->bsfc = NULL;
sti->bsfc = osti->bsfc;
osti->bsfc = NULL;
}
return ret;
}
Expand Down Expand Up @@ -1057,8 +1088,8 @@ static const AVOption options[] = {
{ "segment_atclocktime", "set segment to be cut at clocktime", OFFSET(use_clocktime), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E},
{ "segment_clocktime_offset", "set segment clocktime offset", OFFSET(clocktime_offset), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, 86400000000LL, E},
{ "segment_clocktime_wrap_duration", "set segment clocktime wrapping duration", OFFSET(clocktime_wrap_duration), AV_OPT_TYPE_DURATION, {.i64 = INT64_MAX}, 0, INT64_MAX, E},
{ "segment_time", "set segment duration", OFFSET(time),AV_OPT_TYPE_DURATION, {.i64 = 2000000}, INT64_MIN, INT64_MAX, E },
{ "segment_time_delta","set approximation value used for the segment times", OFFSET(time_delta), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, E },
{ "segment_time", "set segment duration", OFFSET(time),AV_OPT_TYPE_DURATION, {.i64 = 2000000}, 0, INT64_MAX, E },
{ "segment_time_delta","set approximation value used for the segment times", OFFSET(time_delta), AV_OPT_TYPE_DURATION, {.i64 = 0}, INT64_MIN, INT64_MAX, E },
{ "min_seg_duration", "set minimum segment duration", OFFSET(min_seg_duration), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, E },
{ "segment_times", "set segment split time points", OFFSET(times_str),AV_OPT_TYPE_STRING,{.str = NULL}, 0, 0, E },
{ "segment_frames", "set segment split frame numbers", OFFSET(frames_str),AV_OPT_TYPE_STRING,{.str = NULL}, 0, 0, E },
Expand All @@ -1075,6 +1106,8 @@ static const AVOption options[] = {
{ "reset_timestamps", "reset timestamps at the beginning of each segment", OFFSET(reset_timestamps), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E },
{ "initial_offset", "set initial timestamp offset", OFFSET(initial_offset), AV_OPT_TYPE_DURATION, {.i64 = 0}, -INT64_MAX, INT64_MAX, E },
{ "write_empty_segments", "allow writing empty 'filler' segments", OFFSET(write_empty), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E },
{ "segment_write_temp", "write segments as temp files (.tmp) and rename on completion", OFFSET(segment_write_temp), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E },
{ "segment_limit", "stop output once the specified number of segments has been written", OFFSET(segment_limit), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT_MAX, E },
{ NULL },
};

Expand Down