[FFmpeg-devel] [PATCH 3/3] lavf/dashdec: avoid reading the first data segment in read_header

[Steven Liu]

> 2020年5月22日 下午1:42，rcombs <rcombs at rcombs.me> 写道：
> 
> This reduces the number of requests that have to be made during startup.
> ---
> libavformat/dashdec.c | 41 ++++++++++++++++++++++++++---------------
> 1 file changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
> index ec2aadcee3..1bd070c7cb 100644
> --- a/libavformat/dashdec.c
> +++ b/libavformat/dashdec.c
> @@ -1798,6 +1798,19 @@ static int read_data(void *opaque, uint8_t *buf, int buf_size)
>     DASHContext *c = v->parent->priv_data;
> 
> restart:
> +    /* load/update Media Initialization Section, if any */
> +    if ((ret = update_init_section(v)) < 0)
> +        goto end;
> +
> +    if (v->init_sec_buf_read_offset < v->init_sec_data_len) {
> +        /* Push init section out first before first actual fragment */
> +        int copy_size = FFMIN(v->init_sec_data_len - v->init_sec_buf_read_offset, buf_size);
> +        memcpy(buf, v->init_sec_buf, copy_size);
> +        v->init_sec_buf_read_offset += copy_size;
> +        ret = copy_size;
> +        goto end;
> +    }
> +
>     if (!v->input) {
>         free_fragment(&v->cur_seg);
>         v->cur_seg = get_current_fragment(v);
> @@ -1806,11 +1819,6 @@ restart:
>             goto end;
>         }
> 
> -        /* load/update Media Initialization Section, if any */
> -        ret = update_init_section(v);
> -        if (ret)
> -            goto end;
> -
>         ret = open_input(c, v, v->cur_seg);
>         if (ret < 0) {
>             if (ff_check_interrupt(c->interrupt_callback)) {
> @@ -1823,15 +1831,6 @@ restart:
>         }
>     }
> 
> -    if (v->init_sec_buf_read_offset < v->init_sec_data_len) {
> -        /* Push init section out first before first actual fragment */
> -        int copy_size = FFMIN(v->init_sec_data_len - v->init_sec_buf_read_offset, buf_size);
> -        memcpy(buf, v->init_sec_buf, copy_size);
> -        v->init_sec_buf_read_offset += copy_size;
> -        ret = copy_size;
> -        goto end;
> -    }
> -
>     /* check the v->cur_seg, if it is null, get current and double check if the new v->cur_seg*/
>     if (!v->cur_seg) {
>         v->cur_seg = get_current_fragment(v);
> @@ -1940,10 +1939,19 @@ static int reopen_demux_for_component(AVFormatContext *s, struct representation
>     if ((ret = ff_copy_whiteblacklists(pls->ctx, s)) < 0)
>         goto fail;
> 
> +
> +    if (pls->init_sec_data_len <= 0) {
> +        /* load/update Media Initialization Section, if any */
> +        if ((ret = update_init_section(pls)) < 0)
> +            goto fail;
> +    }
> +
>     pls->ctx->flags = AVFMT_FLAG_CUSTOM_IO;
>     pls->ctx->probesize = s->probesize > 0 ? s->probesize : 1024 * 4;
> +    if (pls->init_sec_data_len > 0)
> +        pls->ctx->probesize = FFMIN(pls->ctx->probesize, pls->init_sec_data_len);
>     pls->ctx->max_analyze_duration = s->max_analyze_duration > 0 ? s->max_analyze_duration : 4 * AV_TIME_BASE;
> -    ret = av_probe_input_buffer(&pls->pb, &in_fmt, "", NULL, 0, 0);
> +    ret = av_probe_input_buffer(&pls->pb, &in_fmt, "", NULL, 0, pls->ctx->probesize);
>     if (ret < 0) {
>         av_log(s, AV_LOG_ERROR, "Error when loading first fragment, playlist %d\n", (int)pls->rep_idx);
>         avformat_free_context(pls->ctx);
> @@ -1954,6 +1962,9 @@ static int reopen_demux_for_component(AVFormatContext *s, struct representation
>     pls->ctx->pb = &pls->pb;
>     pls->ctx->io_open  = nested_io_open;
> 
> +    if (pls->init_sec_data_len > 0)
> +        av_dict_set_int(&in_fmt_opts, "header_size", pls->init_sec_data_len, 0);
> +
>     // provide additional information from mpd if available
>     ret = avformat_open_input(&pls->ctx, "", in_fmt, &in_fmt_opts); //pls->init_section->url
>     av_dict_free(&in_fmt_opts);
> -- 
> 2.26.2
> 
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Patchset LGTM

Thanks

Steven Liu