[FFmpeg-devel] [PATCH] avformat/hlsenc: add hls_flag option to create segments atomically

[Aman Gupta]

On Tue, Jan 31, 2017 at 12:29 PM, Aman Gupta <ffmpeg at tmm1.net> wrote:

> From: Aman Gupta <aman at tmm1.net>
>
> Adds a `-hls_flags +temp_file` which will write segment data to
> filename.tmp, and then rename to filename when the segment is complete
> and before the file is added to the m3u8 playlist.
>
> This patch is similar in spirit to one used in Plex's ffmpeg fork, and
> allows a transcoding webserver to ensure incomplete segment files are
> never served up accidentally.
> ---
>  libavformat/hlsenc.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index bd1e684..23b9011 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -76,6 +76,7 @@ typedef enum HLSFlags {
>      HLS_SECOND_LEVEL_SEGMENT_INDEX = (1 << 8), // include segment index
> in segment filenames when use_localtime  e.g.: %%03d
>      HLS_SECOND_LEVEL_SEGMENT_DURATION = (1 << 9), // include segment
> duration (microsec) in segment filenames when use_localtime  e.g.: %%09t
>      HLS_SECOND_LEVEL_SEGMENT_SIZE = (1 << 10), // include segment size
> (bytes) in segment filenames when use_localtime  e.g.: %%014s
> +    HLS_TEMP_FILE = (1 << 11),
>  } HLSFlags;
>
>  typedef enum {
> @@ -915,6 +916,10 @@ static int hls_start(AVFormatContext *s)
>
>      set_http_options(&options, c);
>
> +    if (c->flags & HLS_TEMP_FILE) {
> +        av_strlcat(oc->filename, ".tmp", sizeof(oc->filename));
> +    }
> +
>      if (c->key_info_file) {
>          if ((err = hls_encryption_start(s)) < 0)
>              goto fail;
> @@ -1276,6 +1281,15 @@ static int hls_write_packet(AVFormatContext *s,
> AVPacket *pkt)
>
>          av_write_frame(oc, NULL); /* Flush any buffered data */
>
> +        if (hls->flags & HLS_TEMP_FILE) {
> +            size_t len = strlen(oc->filename);
> +            char final_filename[sizeof(oc->filename)];
> +            av_strlcpy(final_filename, oc->filename, len);
> +            final_filename[len-4] = '\0';
> +            ff_rename(oc->filename, final_filename, s);
>

This doesn't work on windows, since you cannot rename the file while it is
still open. Strangely ff_rename is not logging any errors in this case.


> +            oc->filename[len-4] = '\0';
> +        }
> +
>          new_start_pos = avio_tell(hls->avf->pb);
>          hls->size = new_start_pos - hls->start_pos;
>          ret = hls_append_segment(s, hls, hls->duration, hls->start_pos,
> hls->size);
> @@ -1406,6 +1420,7 @@ static const AVOption options[] = {
>      {"hls_subtitle_path",     "set path of hls subtitles",
> OFFSET(subtitle_filename), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,    E},
>      {"hls_flags",     "set flags affecting HLS playlist and media file
> generation", OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = 0 }, 0, UINT_MAX, E,
> "flags"},
>      {"single_file",   "generate a single media file indexed with byte
> ranges", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SINGLE_FILE }, 0, UINT_MAX,   E,
> "flags"},
> +    {"temp_file", "write segment to temporary file and rename when
> complete", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_TEMP_FILE }, 0, UINT_MAX,   E,
> "flags"},
>      {"delete_segments", "delete segment files that are no longer part of
> the playlist", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_DELETE_SEGMENTS }, 0,
> UINT_MAX,   E, "flags"},
>      {"round_durations", "round durations in m3u8 to whole numbers", 0,
> AV_OPT_TYPE_CONST, {.i64 = HLS_ROUND_DURATIONS }, 0, UINT_MAX,   E,
> "flags"},
>      {"discont_start", "start the playlist with a discontinuity tag", 0,
> AV_OPT_TYPE_CONST, {.i64 = HLS_DISCONT_START }, 0, UINT_MAX,   E, "flags"},
> --
> 2.10.1 (Apple Git-78)
>
>