[Libav-user] Reducing latency of file opening (when playing from http)

[Bjoern Drabeck]

>>
>> When I am opening a file I call avformat_open_input, then after that I
>> call avformat_find_stream_info, and I am timing those calls:
>>
>> 'avformat_open_input':          9.7970 seconds
>> 'avformat_find_stream_info':  0.1080 seconds
>>
>> So for me the problem seems to be avformat_open_input. My testfiles
>> are all around that range, maybe +-2 sec
>
> You mentioned that you read the files using http urls, so isn't there the download time included in the values you measure for avformat_open_input?
>
Yeah sure, it will have to get the data first, but I am wondering if
that amount of data can be reduced, because 10 sec seems quite long to
me for opening, but those probesize etc don't seem to make a
difference.

On the other hand, once I have opened, and I seek to a spot later in
the file, it is so fast it is almost instant.. so that's why I
wondered if the amount of data analyzed/download on initial opening
can be reduced...

> In my case I fill a memory buffer first and then feed that to the avformat functions.
>
> Nevertheless I will time these two functions again. I always assumed that the time is lost in avformat_find_stream_info and not in avformat_open_input, but may be my assumption was wrong.
>

yeah please let me know your findings, am curious to hear...

>>
>> As I mentioned before, changine probesize/analyzeduration from 5000000
>> to 5000 doesn't seem show any visible effect (just ranging within the
>> usual fluctuations of the above timings)
>>
>> Is that what you experienced too?
>
> if I reduce probesize/analyzeduration it does not get faster, but at some point it fails to recognize the streams. At 100000 it does fail most of the time (mpegts h264/aac).
>

for me I can often go down as low as 5000 (or at least 10000) before
it starts failing.. but the timing doesn't seem to change really...

> Which is why I would love to configure all possible settings which can be set before these functions are called.
>

yeah me too...

cheers,
Bjoern