On 5/7/18 1:59 AM, Michael Niedermayer wrote: > On Sun, May 06, 2018 at 06:04:35PM +0000, Dixit, Vishwanath wrote: >> >> >> On 4/28/18 6:38 AM, Michael Niedermayer wrote: >>> On Fri, Apr 27, 2018 at 08:00:23AM +0000, Dixit, Vishwanath wrote: >>>> >>>> >>>> On 4/27/18 5:15 AM, Michael Niedermayer wrote: >>>>> On Thu, Apr 26, 2018 at 11:05:59AM +0000, Dixit, Vishwanath wrote: >>>>>> >>>>>> >>>>>> On 4/26/18 1:04 AM, Michael Niedermayer wrote: >>>>>>> On Tue, Apr 24, 2018 at 02:46:56PM +0530, vdi...@akamai.com wrote: >>>>>>>> From: Vishwanath Dixit <vdi...@akamai.com> >>>>>>>> >>>>>>>> This utility function creates 64-bit NTP time format as per the RFC >>>>>>>> 5905. >>>>>>>> A simple explaination of 64-bit NTP time format is here >>>>>>>> http://www.beaglesoft.com/Manual/page53.htm >>>>>>>> --- >>>>>>>> libavformat/internal.h | 8 ++++++++ >>>>>>>> libavformat/utils.c | 20 ++++++++++++++++++++ >>>>>>>> 2 files changed, 28 insertions(+) >>>>>>>> >>>>>>>> diff --git a/libavformat/internal.h b/libavformat/internal.h >>>>>>>> index 3582682..e9f758f 100644 >>>>>>>> --- a/libavformat/internal.h >>>>>>>> +++ b/libavformat/internal.h >>>>>>>> @@ -240,6 +240,14 @@ void ff_read_frame_flush(AVFormatContext *s); >>>>>>>> uint64_t ff_ntp_time(void); >>>>>>>> >>>>>>>> /** >>>>>>>> + * Get the NTP time stamp formatted as per the RFC-5905. >>>>>>>> + * >>>>>>>> + * @param ntp_time NTP time in micro seconds (since NTP epoch) >>>>>>>> + * @return the formatted NTP time stamp >>>>>>>> + */ >>>>>>>> +uint64_t ff_time_ntp_format(uint64_t ntp_time); >>>>>>>> + >>>>>>>> +/** >>>>>>>> * Append the media-specific SDP fragment for the media stream c >>>>>>>> * to the buffer buff. >>>>>>>> * >>>>>>>> diff --git a/libavformat/utils.c b/libavformat/utils.c >>>>>>>> index c25eab4..b59d426 100644 >>>>>>>> --- a/libavformat/utils.c >>>>>>>> +++ b/libavformat/utils.c >>>>>>>> @@ -4637,6 +4637,26 @@ uint64_t ff_ntp_time(void) >>>>>>>> return (av_gettime() / 1000) * 1000 + NTP_OFFSET_US; >>>>>>>> } >>>>>>>> >>>>>>>> +uint64_t ff_time_ntp_format(uint64_t ntp_time) >>>>>>>> +{ >>>>>>>> + uint64_t ntp_ts, frac_part; >>>>>>>> + uint32_t sec, usec; >>>>>>>> + >>>>>>>> + //current ntp time in seconds and micro seconds >>>>>>> >>>>>>>> + sec = ntp_time / 1000000; >>>>>>> >>>>>>> This can be truncated >>>>>> Yes, but the truncated part is not getting discarded, as the following >>>>>> line is taking care of that. Please correct me if I have not understood >>>>>> what you have intended to say here. >>>>> >>>>> ok, correcting you then :) >>>>> sec is 32bit >>>>> not all values of "ntp_time / 1000000;" fit in 32bit >>>>> there is no check for this it just produces a wrong result >>>> Yes, you are right. But, I can use only the LS 32bits of the result in the >>>> following code. It is a limitation of 64-bit NTP time format and the issue >>>> is going to occur in 2036. Not sure how to handle it here. At most, I can >>>> print a warning message when the result gets truncated. Could you please >>>> suggest any alternative option? >>> >>> i cant make it work after 2036 as that seems what the design is limited at. >>> But the error can be detected and handled >> Yes, the error can be detected and one possible way I can think of handling >> that error, is to truncate LS bits instead of MS bits. But, this solution >> also will not be completely error free. Honestly, I am not able to find any >> useful ways of handling the error, apart from displaying a warning message. >> Request you to let me know if you have any solution in mind. > > I dont know the oppinion of others, but a warning message seems usefull > in this case Thanks for all the review inputs. I have made the suggested updates and have submitted the revised patch set with version V2. > > thx
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