[FFmpeg-devel] [PATCH 3/3] avformat/dashenc: chunk streaming support for low latency use cases

[Jeyapal, Karthick]

On 2/19/18 11:25 AM, vdixit at akamai.com wrote:
> From: Vishwanath Dixit <vdixit at akamai.com>
>
> ---
>  doc/muxers.texi       |  3 +++
>  libavformat/dashenc.c | 26 +++++++++++++++++++++++---
>  2 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/doc/muxers.texi b/doc/muxers.texi
> index d9a5cc0..c156ec0 100644
> --- a/doc/muxers.texi
> +++ b/doc/muxers.texi
> @@ -254,6 +254,9 @@ Use persistent HTTP connections. Applicable only for HTTP output.
>  @item -hls_playlist @var{hls_playlist}
>  Generate HLS playlist files as well. The master playlist is generated with the filename master.m3u8.
>  One media playlist file is generated for each stream with filenames media_0.m3u8, media_1.m3u8, etc.
> + at item -streaming @var{streaming}
> +Enable (1) or disable (0) chunk streaming mode of output. In chunk streaming
> +mode, each frame will be a moof fragment which forms a chunk.
>  @item -adaptation_sets @var{adaptation_sets}
>  Assign streams to AdaptationSets. Syntax is "id=x,streams=a,b,c id=y,streams=d,e" with x and y being the IDs
>  of the adaptation sets and a,b,c,d and e are the indices of the mapped streams.
> diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
> index 0eb4b25..d6474f3 100644
> --- a/libavformat/dashenc.c
> +++ b/libavformat/dashenc.c
> @@ -81,6 +81,7 @@ typedef struct OutputStream {
>      char bandwidth_str[64];
>  
>      char codec_str[100];
> +    int written_len;
>      char filename[1024];
>      char full_path[1024];
>      char temp_path[1024];
> @@ -114,6 +115,7 @@ typedef struct DASHContext {
>      int master_playlist_created;
>      AVIOContext *mpd_out;
>      AVIOContext *m3u8_out;
> +    int streaming;
>  } DASHContext;
>  
>  static struct codec_string {
> @@ -250,7 +252,8 @@ static int flush_dynbuf(OutputStream *os, int *range_length)
>      // write out to file
>      *range_length = avio_close_dyn_buf(os->ctx->pb, &buffer);
>      os->ctx->pb = NULL;
> -    avio_write(os->out, buffer, *range_length);
> +    avio_write(os->out, buffer + os->written_len, *range_length - os->written_len);
> +    os->written_len = 0;
>      av_free(buffer);
>  
>      // re-open buffer
> @@ -960,7 +963,10 @@ static int dash_init(AVFormatContext *s)
>          os->init_start_pos = 0;
>  
>          if (!strcmp(os->format_name, "mp4")) {
> -            av_dict_set(&opts, "movflags", "frag_custom+dash+delay_moov", 0);
> +            if (c->streaming)
> +                av_dict_set(&opts, "movflags", "frag_every_frame+dash+delay_moov", 0);
> +            else
> +                av_dict_set(&opts, "movflags", "frag_custom+dash+delay_moov", 0);
>          } else {
>              av_dict_set_int(&opts, "cluster_time_limit", c->min_seg_duration / 1000, 0);
>              av_dict_set_int(&opts, "cluster_size_limit", 5 * 1024 * 1024, 0); // set a large cluster size limit
> @@ -1155,7 +1161,7 @@ static int dash_flush(AVFormatContext *s, int final, int stream)
>          }
>  
>          if (!c->single_file) {
> -            if (!strcmp(os->format_name, "mp4"))
> +            if (!strcmp(os->format_name, "mp4") && !os->written_len)
>                  write_styp(os->ctx->pb);
>          } else {
>              snprintf(os->full_path, sizeof(os->full_path), "%s%s", c->dirname, os->initfile);
> @@ -1318,6 +1324,19 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
>          av_dict_free(&opts);
>      }
>  
> +    //write out the data immediately in streaming mode
> +    if (c->streaming && !strcmp(os->format_name, "mp4")) {
> +        int len = 0;
> +        uint8_t *buf = NULL;
> +        if (!os->written_len)
> +            write_styp(os->ctx->pb);
> +        avio_flush(os->ctx->pb);
> +        len = avio_get_dyn_buf (os->ctx->pb, &buf);
> +        avio_write(os->out, buf + os->written_len, len - os->written_len);
> +        os->written_len = len;
> +        avio_flush(os->out);
> +    }
> +
>      return ret;
>  }
>  
> @@ -1394,6 +1413,7 @@ static const AVOption options[] = {
>      { "http_user_agent", "override User-Agent field in HTTP header", OFFSET(user_agent), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, E},
>      { "http_persistent", "Use persistent HTTP connections", OFFSET(http_persistent), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, E },
>      { "hls_playlist", "Generate HLS playlist files(master.m3u8, media_%d.m3u8)", OFFSET(hls_playlist), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, E },
> +    { "streaming", "Enable/Disable streaming mode of output. Each frame will be moof fragment", OFFSET(streaming), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, E },
>      { NULL },
>  };
>  
Patchset pushed.

Regards,
Karthick