[Libav-user] about video duration

Tue Dec 10 23:29:34 CET 2013

Hi friends,

The test video I used is a bit large, it's about 100 MB
https://dl.dropboxusercontent.com/u/89678527/Threw%20It%20On%20The%20Ground.avi

2013/12/11 ವಿನೋದ್ Vinod H I <vinvinod at gmail.com>

> 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
>>
>>
>> _______________________________________________
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>>
>>
>>
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>>
>
>
> --
> Vinod H I
>
>
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