[FFmpeg-devel] [PATCH v2] avcodec/pthread_frame, decode: allow errors to happen on draining

[Muhammad Faiz]

On Fri, Apr 28, 2017 at 11:23 PM, Muhammad Faiz <mfcc64 at gmail.com> wrote:
> On Fri, Apr 28, 2017 at 5:55 PM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>> Hi,
>>
>> On Fri, Apr 28, 2017 at 6:19 AM, Muhammad Faiz <mfcc64 at gmail.com> wrote:
>>>
>>> So, all frames and errors are correctly reported in order.
>>> Also limit the numbers of error during draining to prevent infinite loop.
>>>
>>> This fix fate failure with THREADS>=4:
>>>   make fate-h264-attachment-631 THREADS=4
>>> This also reverts a755b725ec1d657609c8bd726ce37e7cf193d03f.
>>>
>>> Suggested-by: wm4, Ronald S. Bultje, Marton Balint
>>> Signed-off-by: Muhammad Faiz <mfcc64 at gmail.com>
>>> ---
>>>  libavcodec/decode.c        | 21 +++++++++++++++++++--
>>>  libavcodec/internal.h      |  3 +++
>>>  libavcodec/pthread_frame.c | 15 +++++++--------
>>>  3 files changed, 29 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
>>> index 6ff3c40..edfae55 100644
>>> --- a/libavcodec/decode.c
>>> +++ b/libavcodec/decode.c
>>> @@ -568,8 +568,24 @@ FF_ENABLE_DEPRECATION_WARNINGS
>>>          avctx->time_base = av_inv_q(av_mul_q(avctx->framerate,
>>> (AVRational){avctx->ticks_per_frame, 1}));
>>>  #endif
>>>
>>> -    if (avctx->internal->draining && !got_frame)
>>> -        avci->draining_done = 1;
>>> +    /* do not stop draining when got_frame != 0 or ret < 0 */
>>> +    if (avctx->internal->draining && !got_frame) {
>>> +        if (ret < 0) {
>>> +            /* prevent infinite loop if a decoder wrongly always return
>>> error on draining */
>>> +            /* reasonable nb_errors_max = maximum b frames + thread count
>>> */
>>> +            int nb_errors_max = 20 + (HAVE_THREADS &&
>>> avctx->active_thread_type & FF_THREAD_FRAME ?
>>> +                                avctx->thread_count : 1);
>>> +
>>> +            if (avci->nb_draining_errors++ >= nb_errors_max) {
>>> +                av_log(avctx, AV_LOG_ERROR, "Too many errors when
>>> draining, this is a bug. "
>>> +                       "Stop draining and force EOF.\n");
>>> +                avci->draining_done = 1;
>>> +                ret = AVERROR_BUG;
>>> +            }
>>> +        } else {
>>> +            avci->draining_done = 1;
>>> +        }
>>> +    }
>>
>>
>> Hm... I guess this is OK, it would be really nice to have a way of breaking
>> in developer builds (e.g. av_assert or so, although I guess technically this
>> could be enabled in prod builds also).
>
> Add av_assert2().
>
>>
>> Also, Marton suggested to return AVERROR_EOF, maybe handle that here also in
>> addition to ret=0?
>
> Modified.
>
> Updated patch attached.
>
> Thank's

>+        } else {
>+            avci->draining_done = 1;
>+            ret = AVERROR_EOF;
>+        }
>+    }
>
>    avci->compat_decode_consumed += ret;

I'm not sure about changing ret. It seems not trivial. So, I drop the
updated patch, and use the original patch.

Thank's