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I have a video that is only one image and an audio track. It is very large and I would like to make it smaller. Since there is only one image/frame, I would think it would be more efficient if only this one frame would be saved and just shown, instead of having a copy of the image in every frame. How can I make such a video with ffmpeg on linux?

So far I have used the command

ffmpeg -i input.mp4 -vcodec libx265 -crf 28 output.mp4

which greatly reduced the size. I am not quite sure how it does it, but since the result is nearly as small as the audio track (that I extracted for comparison), it seems that the condec is a good choice.

However it takes SO much time for the transformation and I have a couple of other videos I would like to transform. Is there a way to speed up the process or choose a different command?

For example I am thinking, whether I could tell ffmpeg that it is just one image and it should just use the n-th frame and not bother with encoding the rest.

EDIT: Using the ideas from Баяр Гончикжапов is used these commands:

file="input.mp4"
ffmpeg -i "$file" -f image2 -frames:v 1 /tmp/tmp.jpg
ffmpeg -i "$file" -i /tmp/tmp.jpg -map 0:a -map 1:v -c:a copy -c:v copy output.mp4

$ mediainfo "$file"         
General
Complete name                            : 1 Hour Epic Music _ Best Of Two Steps From Hell Voll. III.mp4
Format                                   : MPEG-4
Format profile                           : Base Media / Version 2
Codec ID                                 : mp42
File size                                : 134 MiB
Duration                                 : 1h 0mn
Overall bit rate mode                    : Variable
Overall bit rate                         : 308 Kbps
Encoded date                             : UTC 2013-11-28 04:41:00
Tagged date                              : UTC 2013-11-28 04:41:00
gsst                                     : 0
gstd                                     : 3648063
gssd                                     : B5CC58185HH1408390296880239
gshh                                     : r2---sn-9nj-q0ne.googlevideo.com

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline@L3
Format settings, CABAC                   : No
Format settings, ReFrames                : 1 frame
Format settings, GOP                     : M=1, N=60
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1h 0mn
Bit rate                                 : 210 Kbps
Maximum bit rate                         : 2 389 Kbps
Width                                    : 640 pixels
Height                                   : 360 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 24.000 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.038
Stream size                              : 91.3 MiB (68%)
Encoded date                             : UTC 1904-01-01 00:00:00
Tagged date                              : UTC 2013-11-28 04:41:19

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 1h 0mn
Bit rate mode                            : Variable
Bit rate                                 : 96.0 Kbps
Maximum bit rate                         : 102 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 44.1 KHz
Compression mode                         : Lossy
Stream size                              : 41.7 MiB (31%)
Title                                    : IsoMedia File Produced by Google, 5-11-2011
Encoded date                             : UTC 2013-11-28 04:41:10
Tagged date                              : UTC 2013-11-28 04:41:19


$ mediainfo /tmp/output.mp4 
General
Complete name                            : /tmp/output2.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom
File size                                : 42.4 MiB
Duration                                 : 1h 0mn
Overall bit rate mode                    : Constant
Overall bit rate                         : 97.4 Kbps
Encoded date                             : UTC 1904-01-01 00:00:00
Tagged date                              : UTC 1904-01-01 00:00:00
Writing application                      : Lavf57.83.100

Video
ID                                       : 2
Format                                   : JPEG
Codec ID                                 : 6C
Duration                                 : 40ms
Bit rate mode                            : Constant
Bit rate                                 : 4 215 Kbps
Width                                    : 640 pixels
Height                                   : 360 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.732
Stream size                              : 20.6 KiB (0%)
Encoded date                             : UTC 1904-01-01 00:00:00
Tagged date                              : UTC 1904-01-01 00:00:00

Audio
ID                                       : 1
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 1h 0mn
Bit rate mode                            : Constant
Bit rate                                 : 96.0 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 44.1 KHz
Compression mode                         : Lossy
Stream size                              : 41.7 MiB (99%)
Encoded date                             : UTC 1904-01-01 00:00:00
Tagged date                              : UTC 1904-01-01 00:00:00
  • However, as one can notice, the audio was not really copied. How can I make sure, audio is really copied?
  • Also VLC Player has an issue: When starting the video, the slides (that indicates the time) does not move. If I move it to something greater than 00:00, it does move again...
  • How do I say that I want to extract a different frame than the first?
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1 Answer 1

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Convert one video frame to temporary file, then join temp file with audio:

ffmpeg -i input.mp4 -frames:v 1 -map 0:v -c:v libx265 -crf 18 -y tmp.mp4
ffmpeg -i input.mp4 -i tmp.mp4 -map 0:a -map 1 -c:a copy -c:v copy -y output.mp4

These lines create a video incompatible with the VLC player. Therefore, I propose an option with converting to MP3.

ffmpeg -i input.mp4 -f image2 -frames:v 1 -y /tmp/tmp.jpg
ffmpeg -i input.mp4 -i /tmp/tmp.jpg -map 0:a -map 1 -c:a libmp3lame -c:v copy -y /tmp/output.mp3
vlc /tmp/output.mp3
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  • This would be a better answer if it included an explanation of what the commands do. Yes, it’s kind-of obvious, but this is supposed to be a knowledge base. … … … … … … … … … … … Please do not respond in comments; edit your answer to make it clearer and more complete.
    – Scott - Слава Україні
    Commented Nov 14, 2020 at 8:18
  • This answer indeed includes very little explanation of what is going on here. Also, it'll create an MJPEG-encoded video, which may or may not be what the OP wants.
    – slhck
    Commented Nov 14, 2020 at 9:49
  • Thank you, I tried it out, but I when I played output.mp4 in VLC Player I only got the audio - no image. What might be wrong? How can I check if tmp.mp4 was created correctly?
    – Make42
    Commented Nov 14, 2020 at 20:24
  • @Make42 ffplay and mpv plays output.mp4 correctly, but not vlc. It needs to come up with a way to make it work in vlc. ffplay tmp.mp4 works ok.
    – Баяр Гончикжапов
    Commented Nov 15, 2020 at 3:00
  • So, the extraction of the jpg worked. But the result of the second command is only audio it seems. During conversion it said that h264 is used, but mediainfo /tmp/output.mp3 just says that Format MPEG Audio. My VLC is able to play h265 encoded videos though. I tried combining your first command of your second idea with the second command of your first idea. This gave me a JPEG video (see question edit) and also changed audio, even though I said "copy". I would like that audio is not changed.
    – Make42
    Commented Nov 16, 2020 at 11:14

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