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

[Ridley Combs]

> On May 25, 2020, at 08:43, Gorilla Maguila <gorilla.maguila at gmail.com> wrote:
> 
> 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

Apply the patch series in the order it was sent: http://ffmpeg.org/pipermail/ffmpeg-devel/2020-May/263099.html <http://ffmpeg.org/pipermail/ffmpeg-devel/2020-May/263099.html>
> 
> 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
>>> 
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>>> 
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>> 
>> Patchset LGTM
>> 
>> Thanks
>> 
>> Steven Liu
>> 
>> 
>> 
>> _______________________________________________
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>> 
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>> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
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