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• ffmpeg extract keyframes from certain time ranges to filenames with timestamps from original video

  17 mai 2023, par Display Name

  I have as input specific timestamps I'm interested in, and I wish to extract keyframes closest to them. I thus use skip_frame nokey and a select='between(t,...,...)+between(t,...,...)+...' where I add a few seconds around each time I'm interested in (enough so that at least one keyframe will fall in that range based on the input video I have, and then can manually delete if more than one came out in a given time range in my sequence). Chaining the between()s lets me use a single command to extract all of these images in order to avoid seeking from the beginning of the video for each image, were I to use separate command per image. So this part works fine.

  


  The problem is that I want the output image filenames to correspond to the timestamps, in seconds (or some decimal fraction of seconds like tenths or milliseconds) of the extracted frames with respect to the INPUT video. With older versions of ffmpeg, I used to be able for example to get output filenames being times in terms of tenths of a second with -vsync 0 -r 10 -frame_pts true %05d.webp but with recent versions, that results in the error One of -r/-fpsmax was specified together a non-CFR -vsync/-fps_mode. This is contradictory. Replacing the deprecated -vsync with -fps_mode and one of the CFR values results in ffmpeg DUPLICATING frames to fulfill the specified -r value which results in a huge number of output images. The way I am able to get just the set of keyframes I want and no duplications is to drop the -r and use -fps_mode passthrough, but then I lose the naming of the output files by their time in the original video. Searching around here and elsewhere on the web, I have tried things like setting settb=...,setpts=... and -copyts but in the end couldn't get it to work.

  


  As a complete example, the command
ffmpeg -skip_frame nokey -i "input.mp4" -vf "select='between(t,15,25)+between(t,40,50)+between(t,95,105)+between(t,120,130)+between(t,190,200)',scale='min(480,iw)':-2:flags=lanczos" -fps_mode passthrough -copyts -c:v libwebp -quality 75 -preset photo -frame_pts true %05d.webp gives me the right set of output images, but not the filenames that would make it easy for me to quickly manually find frames corresponding to specific times in the original video.

  


• ffmpeg : how to extract keyframes from certain time ranges into filenames with timestamps from the original video ?

  18 mai 2023, par Display Name

  I have as input specific timestamps I'm interested in, and I wish to extract keyframes closest to them. I thus use skip_frame nokey and a select='between(t,...,...)+between(t,...,...)+...' where I add a few seconds around each time I'm interested in (enough so that at least one keyframe will fall in that range based on the input video I have, and then can manually delete if more than one came out in a given time range in my sequence). Chaining the between()s lets me use a single command to extract all of these images in order to avoid seeking from the beginning of the video for each image, were I to use separate command per image. So this part works fine.

  


  The problem is that I want the output image filenames to correspond to the timestamps, in seconds (or some decimal fraction of seconds like tenths or milliseconds) of the extracted frames with respect to the INPUT video. With older versions of ffmpeg, I used to be able for example to get output filenames being times in terms of tenths of a second with -vsync 0 -r 10 -frame_pts true %05d.webp but with recent versions, that results in the error One of -r/-fpsmax was specified together a non-CFR -vsync/-fps_mode. This is contradictory. Replacing the deprecated -vsync with -fps_mode and one of the CFR values results in ffmpeg DUPLICATING frames to fulfill the specified -r value which results in a huge number of output images. The way I am able to get just the set of keyframes I want and no duplications is to drop the -r and use -fps_mode passthrough, but then I lose the naming of the output files by their time in the original video. Searching around here and elsewhere on the web, I have tried things like setting settb=...,setpts=... and -copyts but in the end couldn't get it to work.

  


  As a complete example, the command
ffmpeg -skip_frame nokey -i "input.mp4" -vf "select='between(t,15,25)+between(t,40,50)+between(t,95,105)+between(t,120,130)+between(t,190,200)',scale='min(480,iw)':-2:flags=lanczos" -fps_mode passthrough -copyts -c:v libwebp -quality 75 -preset photo -frame_pts true %05d.webp gives me the right set of output images, but not the filenames that would make it easy for me to quickly manually find frames corresponding to specific times in the original video.

  


• Audio PTS is not equal but play time is equal

  20 juillet 2023, par KaGa Wu

  I have a video which has an dubbed Portuguese audio stream. The stream does not have the video head, like BGM of companies playing logos. So, the audio stream to delay some time play, it's first data package PTS is 9s. Then I transcode the audio stream to AAC, it's first package PTS is 2s. In my thinking the audio stream put the first data package in more front, it will play in more front originally, but it plays delay time is right !

  


  Here is the first package PTS, origin and transcoded.

  


  origin

  


  https://files.videohelp.com/u/302682/025_sisu_hevc_1920x800_30s_yuv420p_aac_copy.ts

  


  0x00458B74 Transport Packet { PID = 0x101, Payload = Yes (182), Counter = 15, Start indicator }
Adaptation Field ():
adaptation_field_length = 1
discontinuity_indicator = 0
random_access_indicator = 1
elementary_stream_priority_indicator = 0
PCR_flag = 0
OPCR_flag = 0
splicing_point_flag = 0
transport_private_data_flag = 0
adaptation_field_extension_flag = 0

0x00458B7A PES Packet { stream_id = 0xC0  (audio stream)}
packet_length = 2898
PES_scrambling_control = 0
PES_priority = 0
data_alignment_indicator = 0
copyright = 0
original_or_copy = 0
PTS_DTS_flags = 2
ESCR_flag = 0
ES_rate_flag = 0
DSM_trick_mode_flag = 0
additional_copy_info_flag = 0
PES_CRC_flag = 0
PES_extension_flag = 0
PES_header_data_length = 5
 PTS =  0:  0:  9: 570 (861 300)

0x00458B88 AAC Frame
id = 0
layer = 0
protection_absent = 1
profile = 1
sf_index = 3
private_bit = 0
channel_configuration = 6
original = 0
home = 0
copyright_identification_bit = 0
copyright_identification_start = 0
aac_frame_length = 285
adts_buffer_fullness = 2047
no_raw_data_blocks_in_frame = 0
SamplingRate = 48000
Channels = 6
Duration = 0.021333


  


  transcoded

  


  https://files.videohelp.com/u/302682/025_susi_hevc_1920x800_30s_yuv420p_aac_trans.ts

  


  0x000010E4 Transport Packet { PID = 0x101, Payload = Yes (182), Counter = 0, Start indicator }
Adaptation Field ():
adaptation_field_length = 1
discontinuity_indicator = 0
random_access_indicator = 1
elementary_stream_priority_indicator = 0
PCR_flag = 0
OPCR_flag = 0
splicing_point_flag = 0
transport_private_data_flag = 0
adaptation_field_extension_flag = 0

0x000010EA PES Packet { stream_id = 0xC0  (audio stream)}
packet_length = 467
PES_scrambling_control = 0
PES_priority = 0
data_alignment_indicator = 0
copyright = 0
original_or_copy = 0
PTS_DTS_flags = 2
ESCR_flag = 0
ES_rate_flag = 0
DSM_trick_mode_flag = 0
additional_copy_info_flag = 0
PES_CRC_flag = 0
PES_extension_flag = 0
PES_header_data_length = 5
 PTS =  0:  0:  1: 400 (126 000)

0x000010F8 AAC Frame
id = 0
layer = 0
protection_absent = 1
profile = 1
sf_index = 3
private_bit = 0
channel_configuration = 6
original = 0
home = 0
copyright_identification_bit = 0
copyright_identification_start = 0
aac_frame_length = 43
adts_buffer_fullness = 2047
no_raw_data_blocks_in_frame = 0
SamplingRate = 48000
Channels = 6
Duration = 0.021333


  


  I decode the origin video and transcoded video，and print screen of them.