[FFmpeg-devel] [PATCH 3/4] libavformat/segment: add an option to write the header to a separate file

[Stefano Sabatini]

On date Saturday 2015-03-28 19:25:20 -0600, Rodger Combs encoded:
> This permits some interesting segmenting techniques with formats like Matroska,
> where you can concatenate the header and segments [N, nb_segments) and get
> a working file that starts at segment N's start time.
> ---
>  libavformat/segment.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/libavformat/segment.c b/libavformat/segment.c
> index b623bb6..b84b2df 100644
> --- a/libavformat/segment.c
> +++ b/libavformat/segment.c
> @@ -105,6 +105,7 @@ typedef struct SegmentContext {
>      int64_t time_delta;
>      int  individual_header_trailer; /**< Set by a private option. */
>      int  write_header_trailer; /**< Set by a private option. */
> +    char *header_filename;  ///< filename to write the output header to
>  
>      int reset_timestamps;  ///< reset timestamps at the begin of each segment
>      int64_t initial_offset;    ///< initial timestamps offset, expressed in microseconds
> @@ -594,6 +595,11 @@ static int seg_write_header(AVFormatContext *s)
>      if (!seg->write_header_trailer)
>          seg->individual_header_trailer = 0;
>  
> +    if (seg->header_filename) {
> +        seg->write_header_trailer = 1;
> +        seg->individual_header_trailer = 0;
> +    }
> +
>      if (!!seg->time_str + !!seg->times_str + !!seg->frames_str > 1) {
>          av_log(s, AV_LOG_ERROR,
>                 "segment_time, segment_times, and segment_frames options "
> @@ -670,7 +676,7 @@ static int seg_write_header(AVFormatContext *s)
>          goto fail;
>  
>      if (seg->write_header_trailer) {
> -        if ((ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
> +        if ((ret = avio_open2(&oc->pb, seg->header_filename ? seg->header_filename : oc->filename, AVIO_FLAG_WRITE,
>                                &s->interrupt_callback, NULL)) < 0) {
>              av_log(s, AV_LOG_ERROR, "Failed to open segment '%s'\n", oc->filename);
>              goto fail;
> @@ -706,8 +712,13 @@ static int seg_write_header(AVFormatContext *s)
>      if (oc->avoid_negative_ts > 0 && s->avoid_negative_ts < 0)
>          s->avoid_negative_ts = 1;
>  
> -    if (!seg->write_header_trailer) {
> -        close_null_ctxp(&oc->pb);
> +    if (!seg->write_header_trailer || seg->header_filename) {
> +        if (seg->header_filename) {
> +            av_write_frame(oc, NULL);
> +            avio_closep(&oc->pb);
> +        } else {
> +            close_null_ctxp(&oc->pb);
> +        }
>          if ((ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
>                                &s->interrupt_callback, NULL)) < 0)
>              goto fail;
> @@ -880,6 +891,7 @@ static const AVOption options[] = {
>      { "segment_format",    "set container format used for the segments", OFFSET(format),  AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       E },
>      { "segment_format_options", "set list of options for the container format used for the segments", OFFSET(format_options_str), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, E },
>      { "segment_list",      "set the segment list filename",              OFFSET(list),    AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       E },
> +    { "segment_header_filename", "write a single file containing the header", OFFSET(header_filename), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, E },

Please send a patch updating the manual with an use case.
-- 
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