From the screenshot above, the frame rate of the video is 30 fps. This means that 30 images will be extracted for every second of the video when running the basic command ffmpeg -i input.mp4 %04d.png. As a result, a total of 274 images will be generated from the input video.
say i have four .mp4 file where 2 of them doesn't have audio track (because those are image based video clip). when i try to concat using below code, the output is totally different where the audio of 4.ts starts playing when video of 2.ts start or in other words the audio files are left-aligning and i guess there is something i need to play with -map but not sure how to fix it.
You can check if the video files that are not playing have modified dates. In the same vein, make sure that you take precautions when downloading video files. This is because hackers sometimes cleverly sneak in viruses. For example, you might be tempted to download a video file with a .mp4.exe. The bad news is that this file might appear like a normal MP4 video file but the genuine files have a suffix that looks like.EXE.
Note that these are not two different pieces of video content, or a playlist; rather, they are the same video, provided in two different codecs. Browsers that support webm will preferentially download the (smaller, faster to load) .webm file; browsers that do not will load the .mp4 version. Attributes in the video tag will apply to both versions. 041b061a72