| Message ID | 1524561418-4419-1-git-send-email-vdixit@akamai.com |
|---|---|
| State | Superseded |
| Headers | show |
On Tue, Apr 24, 2018 at 02:46:56PM +0530, vdixit@akamai.com wrote: > From: Vishwanath Dixit <vdixit@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 > + usec = ntp_time % 1000000; > + > + //encoding in ntp timestamp format > + frac_part = usec * 0xFFFFFFFFULL; > + frac_part /= 1000000; > + > + ntp_ts = (uint64_t) sec; > + ntp_ts <<= 32; > + ntp_ts |= frac_part; > + > + return ntp_ts; this looks similar to what av_rescale does. also ff_time_ntp_format() is a bad name. It does not give any hint on if ntp time is the input or output of the call [...]
On 4/26/18 1:04 AM, Michael Niedermayer wrote: > On Tue, Apr 24, 2018 at 02:46:56PM +0530, vdixit@akamai.com wrote: >> From: Vishwanath Dixit <vdixit@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. > > >> + usec = ntp_time % 1000000; >> + >> + //encoding in ntp timestamp format >> + frac_part = usec * 0xFFFFFFFFULL; >> + frac_part /= 1000000; >> + >> + ntp_ts = (uint64_t) sec; >> + ntp_ts <<= 32; >> + ntp_ts |= frac_part; >> + >> + return ntp_ts; > > this looks similar to what av_rescale does. Not really. This is a unique format as defined in RFC 5905. (please see this page for high level understanding of this format http://www.beaglesoft.com/Manual/page53.htm ) > > > also ff_time_ntp_format() is a bad name. It does not give any hint > on if ntp time is the input or output of the call Okay. I will submit a revised patch with a more meaningful function name. How does 'ff_get_formatted_ntp_time' sound like? > > [...] > > > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
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, vdixit@akamai.com wrote: > >> From: Vishwanath Dixit <vdixit@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 > > > > > >> + usec = ntp_time % 1000000; > >> + > >> + //encoding in ntp timestamp format > >> + frac_part = usec * 0xFFFFFFFFULL; > >> + frac_part /= 1000000; > >> + > >> + ntp_ts = (uint64_t) sec; > >> + ntp_ts <<= 32; > >> + ntp_ts |= frac_part; > >> + > >> + return ntp_ts; > > > > this looks similar to what av_rescale does. > Not really. This is a unique format as defined in RFC 5905. (please see this page for high level understanding of this format http://www.beaglesoft.com/Manual/page53.htm ) it still looks very similar to me. But lets keep your code. if you prefer. [...]
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, vdixit@akamai.com wrote: >>>> From: Vishwanath Dixit <vdixit@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? > > >>> >>> >>>> + usec = ntp_time % 1000000; >>>> + >>>> + //encoding in ntp timestamp format >>>> + frac_part = usec * 0xFFFFFFFFULL; >>>> + frac_part /= 1000000; >>>> + >>>> + ntp_ts = (uint64_t) sec; >>>> + ntp_ts <<= 32; >>>> + ntp_ts |= frac_part; >>>> + >>>> + return ntp_ts; >>> >>> this looks similar to what av_rescale does. >> Not really. This is a unique format as defined in RFC 5905. (please see this page for high level understanding of this format http://www.beaglesoft.com/Manual/page53.htm ) > > it still looks very similar to me. But lets keep your code. if you prefer. Okay, let's keep the code, otherwise I will not be able to get the expected functionality using av_rescale function. > > [...] > > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
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, vdixit@akamai.com wrote: > >>>> From: Vishwanath Dixit <vdixit@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 [...]
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, vdixit@akamai.com wrote: >>>>>> From: Vishwanath Dixit <vdixit@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. > > [...] > > > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
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, vdixit@akamai.com wrote: > >>>>>> From: Vishwanath Dixit <vdixit@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 thx [...]
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, vdixit@akamai.com wrote: >>>>>>>> From: Vishwanath Dixit <vdixit@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
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; + usec = ntp_time % 1000000; + + //encoding in ntp timestamp format + frac_part = usec * 0xFFFFFFFFULL; + frac_part /= 1000000; + + ntp_ts = (uint64_t) sec; + ntp_ts <<= 32; + ntp_ts |= frac_part; + + return ntp_ts; +} + int av_get_frame_filename2(char *buf, int buf_size, const char *path, int number, int flags) { const char *p;
From: Vishwanath Dixit <vdixit@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(+)