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

[Gorilla Maguila]

These lines:

+    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);


cause an Error in av_probe_input_buffer when pls->init_sec_data_len
or pls->ctx->probesize are < 2048 due to the following line in
av_probe_input_buffer:

https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/format.c#L236

El vie., 22 may. 2020 a las 9:22, Steven Liu (<lq at chinaffmpeg.org>)
escribió:

>
>
> > 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
> >
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>
> Patchset LGTM
>
> Thanks
>
> Steven Liu
>
>
>
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