[Libav-user] is it possible to get a decode error

[Anton Shekhovtsov]

2017-07-13 11:18 GMT+03:00 jing zhang <zhangjing.lm at gmail.com>:

> 1) The decoder call the log callback synchronous when it encounter a error
> or other messages. You can change the code to log the frame number? Like
> h.264, slice header has a frame_num
> 2) You can use AVClass->class_name to check which context logger using.
> Use AVCodecContext->opaque to save your information about which decoder you
> are using.
>
> 2017-07-13 16:02 GMT+08:00 Anton Shekhovtsov <shekh.anton at gmail.com>:
>
>>
>>
>> 2017-07-13 4:31 GMT+03:00 jing zhang <zhangjing.lm at gmail.com>:
>>
>>> Hi,
>>>
>>> Try set your own log callback (use av_log_set_callback), and check
>>> errors in your call back function.
>>>
>>> zj
>>>
>>> 2017-07-12 19:13 GMT+08:00 Anton Shekhovtsov <shekh.anton at gmail.com>:
>>>
>>>> I expected avcodec_receive_frame to return any kind of error code when
>>>> something goes wrong with a decoding. However it always returns success, I
>>>> can only guess there is something wrong by side effects (decoded frame not
>>>> updated, messages in log).
>>>> Is this feature supported?
>>>>
>>>>
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>>>>
>>>
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>>>
>> Hi, Thanks for reply, however I don't think log callback can solve this:
>> 1) Decoding is asynchronous, not possible to know which frame is affected
>> from log message. Even If I knew it, the mechanism to deliver the result to
>> a point where it is needed (code calling avcodec_receive_frame) would be
>> ugly and complex.
>> 2) Not sure log message is even associated with specific context.
>> According to docs maybe it has a pointer to pointer to AVClass (how is that
>> useful?) or not. Seems like log callback captures messages of the whole
>> library, so if I do multiple operations on different threads how to tell
>> which one had errors?
>>
>>
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>>
>
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>
1) Do you mean, can I change libavcodec sources? I'm trying to avoid it.
>From some examples I looked into, seems too much trouble:
ffv1dec.c
av_log(f->avctx, AV_LOG_ERROR, "CRC mismatch %X!", crc);
To know which frame is related to log message, I must extend log callback
protocol, and update all relevant av_log calls. If it is like that with
every decoder I'd rather leave it alone.

2) This gives me some idea to try, thanks!
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