AI Is Slowing Down Tracker

There are infinite similar use cases.

I guess the killer app (for AI coding) will be a framework to successfully structure projects in appropriately sized complexity morsels LLMs can efficiently chew through.

- Has Amazon’s Kiro truly managed this?

- What other efforts are there in this direction?

I would try it again without the pix_fmt flag, the vf flag (and string). No idea what -level 3.0 is as it’s not in the docs anywhere (hallucination?). The video filter scaling definitely needs to go if you want it to be as close to the original resolution.

Cool part is, it worked. Even with a bad flag or two, ffmpeg said “Hold my beer”

<< On the ffmpeg command,

• It’s conservative but works. The key bits for web playback are: H.264 video, yuv420p, AAC audio, MP4 container with +faststart. That’s exactly what it ensures.

• Where it’s sub‑optimal in 2025:

• profile/level: baseline, level 3.0 maximizes legacy compatibility but hurts efficiency/quality (no B‑frames, CABAC, etc.). High, level 4.0 (or auto) is widely supported on modern browsers/devices.

• quality control: better to use CRF + preset than implicit defaults. Example: -crf 20 -preset veryfast (or slow if you can wait).

• scaling: forcing even dimensions is fine; you can also just let libx264 pad/scale as needed or do scale=ceil(iw/2)2:ceil(ih/2)2 to avoid rounding down.

• redundancy: -pix_fmt yuv420p is good; adding format=yuv420p in -vf is redundant if -pix_fmt is set.

• Practical “ladder” that minimizes work and preserves quality:

1. If codecs already web‑friendly, just remux: ffmpeg -i in.mkv -c copy -movflags +faststart out.mp4 (Works when video is H.264 yuv420p and audio is AAC.)

2. If video is OK but audio isn’t (e.g., AC3/Opus), transcode audio only: ffmpeg -i in.mkv -c:v copy -c:a aac -b:a 160k -movflags +faststart out.mp4

3. If video needs re-encode, use modern defaults: ffmpeg -i in.mkv -c:v libx264 -profile:v high -level 4.0 -pix_fmt yuv420p -crf 20 -preset veryfast -vf “scale=ceil(iw/2)2:ceil(ih/2)2” -c:a aac -b:a 160k -movflags +faststart out.mp4

4. If you have GPU/QSV and just need “good enough” fast: ffmpeg -hwaccel auto -i in.mkv -c:v h264_nvenc -preset p5 -rc vbr -cq 23 -b:v 5M -maxrate 8M -bufsize 10M -profile:v high -pix_fmt yuv420p -c:a aac -b:a 160k -movflags +faststart out.mp4

• Quick verification after transcoding: ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,profile,level,pix_fmt,width,height -of default=nw=1 out.mp4 >>

This just to say anything that is more than a couple flag usually find themselves as alias, function, or shell script.

> I could look up all those flags, but I haven't. But the command did seem to work! I'm sure the HN crowd can critique. =)

Not critique. But just highlighting that ffmpeg is a power tool. Most of the intricacies are codecs and audio/video knowledge. Not ffmpeg itself. You have stuff like containers, video codecs, audio codecs, audio channels, media tracks, resolution, bitrate, quality (lossy), compression rate (lossless),... and a bunc h of manipulation depending on the media type.

Just for you to know, H.264 (the standard) is one of the most supported video format, playable on anything not from the stone age, it's successor is H.265 (which restarted the license controversy) which is mostly used for 4k media on the sea. Then you need a container (MP4) that can contains both the video and audio track. MKV is another type of container. yuv420 is how color is represented (Chroma subsampling), much better than RGB when you want free compression. faststart is to be able to start playing the media as soon as possible, instead of having to download a good part of the file. I think PDF have something like that too.