[Libav-user] about video duration

Tue Dec 10 15:00:19 CET 2013

It would be better if you can give a link to the test video file also.

On Tue, Dec 10, 2013 at 6:29 PM, Safi ud Din Khan
<safiuddinkhan at gmail.com>wrote:

>  I can understand its all extremely confusing .... i have also been to
> this stuff it took me  5 moths just to understand how everything worked
> .....
>
> my advice to you you is that you should atlest read about how mpeg 2
> compression works .... mpeg4 , h264 and other compression are quiet complex
> but at their core they work pretty much like mpeg 2 compression
>
> atlest concern mpeg2 part in this book its bit out dated but you would
> understand that how everything works
>
>
> https://dl.dropboxusercontent.com/u/15671916/video%20compression/DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf
>
> you dont need to have to go too deep to understand video decoding/encoding
> ... ffmpeg library will do much for you ... just get some of how mpeg 2
> codec works
>
> On 12/10/2013 12:14 PM, YIRAN LI wrote:
>
> Hi friends,
>
>
>  I'm now checking a duration issue of a video file.
> Here is some trace print out when file is opened, so we can know the dts
> of last AVPacket is 167542, and the last frame  time stamp = 167376, and
> coded_picture_num = 4013
>
>
>    Line 100: 00:00:33.384 MAIN rhbc73 process packet, Packet.dts = 0,
> Packet.pts = -9223372036854775808 Line 101: 00:00:33.384 MAIN rhbc73
> process packet, Packet.dts = 42, Packet.pts = -9223372036854775808 Line
> 102: 00:00:33.400 MAIN rhbc73 process packet, Packet.dts = 83, Packet.pts =
> -9223372036854775808 Line 103: 00:00:33.400 MAIN rhbc73 process packet,
> Packet.dts = 125, Packet.pts = -9223372036854775808 Line 104: 00:00:33.400
> MAIN rhbc73 process packet, Packet.dts = 167, Packet.pts =
> -9223372036854775808 Line 105: 00:00:33.400 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 0, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 0, pFrame->coded_picture_number = 0 Line 107:
> 00:00:33.400 MAIN rhbc73 process packet, Packet.dts = 209, Packet.pts =
> -9223372036854775808 Line 108: 00:00:33.400 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 42, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 42, pFrame->coded_picture_number = 1 Line 110:
> 00:00:33.400 MAIN rhbc73 process packet, Packet.dts = 250, Packet.pts =
> -9223372036854775808 Line 111: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 83, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 83, pFrame->coded_picture_number = 2 Line 113:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 292, Packet.pts =
> -9223372036854775808 Line 114: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 125, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 125, pFrame->coded_picture_number = 3 Line 116:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 334, Packet.pts =
> -9223372036854775808 Line 117: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 167, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 167, pFrame->coded_picture_number = 4 Line 119:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 375, Packet.pts =
> -9223372036854775808 Line 120: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 209, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 209, pFrame->coded_picture_number = 5 Line 122:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 417, Packet.pts =
> -9223372036854775808 Line 123: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 250, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 250, pFrame->coded_picture_number = 6 Line 125:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 459, Packet.pts =
> -9223372036854775808 Line 126: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 292, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 292, pFrame->coded_picture_number = 7 Line 128:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 501, Packet.pts =
> -9223372036854775808 Line 129: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 334, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 334, pFrame->coded_picture_number = 8 Line 131:
> 00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 542, Packet.pts =
> -9223372036854775808 Line 132: 00:00:33.416 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 375, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 375, pFrame->coded_picture_number = 9 Line 12134:
> 00:00:51.168 MAIN rhbc73 process packet, Packet.dts = 167417, Packet.pts =
> -9223372036854775808 Line 12135: 00:00:51.168 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 167250, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 167250, pFrame->coded_picture_number = 4010 Line
> 12137: 00:00:51.168 MAIN rhbc73 process packet, Packet.dts = 167459,
> Packet.pts = -9223372036854775808 Line 12138: 00:00:51.168 MAIN rhbc73 --
> get a full frame, pFrame->pkt_dts = 167292, pFrame->pkt_pts =
> -9223372036854775808, BestEffortTimeStamp = 167292,
> pFrame->coded_picture_number = 4011 Line 12140: 00:00:51.168 MAIN rhbc73
> process packet, Packet.dts = 167501, Packet.pts = -9223372036854775808 Line
> 12141: 00:00:51.168 MAIN rhbc73 -- get a full frame, pFrame->pkt_dts =
> 167334, pFrame->pkt_pts = -9223372036854775808, BestEffortTimeStamp =
> 167334, pFrame->coded_picture_number = 4012 Line 12143: 00:00:51.184 MAIN
> rhbc73 process packet, Packet.dts = 167542, Packet.pts =
> -9223372036854775808 Line 12144: 00:00:51.184 MAIN rhbc73 -- get a full
> frame, pFrame->pkt_dts = 167376, pFrame->pkt_pts = -9223372036854775808,
> BestEffortTimeStamp = 167376, pFrame->coded_picture_number = 4013
>
>  But when I check the file using ffprobe -show_frames -select_streams v
> input I could see
>
>   [FRAME]
> media_type=video
> key_frame=0
> pkt_pts=N/A
> pkt_pts_time=N/A
> pkt_dts=167501
> pkt_dts_time=167.501000
> pkt_duration=N/A
> pkt_duration_time=N/A
> pkt_pos=103794518
> pkt_size=74
> width=1920
> height=1080
> pix_fmt=yuv420p
> sample_aspect_ratio=1:1
> pict_type=P
> coded_picture_number=4016
> display_picture_number=0
> interlaced_frame=0
> top_field_first=0
> repeat_pict=0
> [/FRAME]
> [FRAME]
> media_type=video
> key_frame=0
> pkt_pts=N/A
> pkt_pts_time=N/A
>  pkt_dts=167542
> pkt_dts_time=167.542000
> pkt_duration=N/A
> pkt_duration_time=N/A
> pkt_pos=103794920
> pkt_size=74
> width=1920
> height=1080
> pix_fmt=yuv420p
> sample_aspect_ratio=1:1
> pict_type=P
> coded_picture_number=4017
> display_picture_number=0
> interlaced_frame=0
> top_field_first=0
> repeat_pict=0
> [/FRAME]
>
>  the ffprobe and ffmpeg libs were built from same latest source, so I'd
> like to know why ffprobe could dump a last frame of timestamp 167542 but
> av_read_frame + avcodec_decode_video2
>  couldn't
>
>
>  Thanks
>
>
> _______________________________________________
> Libav-user mailing listLibav-user at ffmpeg.orghttp://ffmpeg.org/mailman/listinfo/libav-user
>
>
>
> _______________________________________________
> Libav-user mailing list
> Libav-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/libav-user
>
>

-- 
Vinod H I
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ffmpeg.org/pipermail/libav-user/attachments/20131210/09a95d19/attachment.html>