SPARCHER.TechBlog: FFmpeg

Showing posts with label FFmpeg. Show all posts

2017-12-28

HOWTO: grab online video stream with FFmpeg

Usually, it's quite easy to save some free online (live) video streams with FFmpeg.

Example: grabbing some HLS stream with MPEG-4 (H.264) video and AAC (or MP3) audio.

$ ffmpeg -i "http://some.streaming.server/favorite_stream.m3u8" -codec copy -f mpegts stream01.ts

(Generally, the output format can be guessed by extension automatically, so we can shorten the command line).

$ ffmpeg -i "http://some.streaming.server/favorite_stream.m3u8" -codec copy stream02.ts

The TS file is usually playable during download.
Usually, you can stop the grabbing operation at any time by pressing the <q> key.
After the stream dumping is finished, you can convert (remux) your video to a more familiar MP4 container format.

$ ffmpeg -i stream01.ts -codec copy stream01.mp4

(Usually, you'd prefer a playback-optimized output file).

$ ffmpeg -i stream02.ts -codec copy -movflags faststart stream02.mp4

Reference:

FFmpeg Formats Documentation

2017-12-25

HOWTO: optimize MP4 video for fast loading with FFmpeg

MP4 video loading can be accelerated (e. g., allowing playback of partially downloaded videos for end users) by moving the metadata (the "moov atom") to the beginning of the file. And that's a lossless procedure (no video, audio or subtitle data gets lost; may alter some metadata though)!

Can be performed very fast and easily with the qt-faststart utility (targeted primarily at Apple QuickTime MOV files, but should work for most MP4 base media files too); you can find that utility in your favorite FFmpeg distribution.
```
$ qt-faststart in01.mov out01.mov
$ qt-faststart in02.mp4 out02.mp4
```
More thorough (but a little bit slower) method involves the universal ffmpeg program to remux the original video:
```
$ ffmpeg -i in10.mp4 -codec copy -movflags faststart out10.mp4
```

Reference:

FFmpeg Formats Documentation

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Last updated: 2018-03-01

2015-09-30

HOWTO: get rid of packed B-frames in AVI (MPEG-4 Visual) video with FFmpeg

You've probably seen some AVI (Audio Video Interleave) files with MPEG-4 video (more specifically, MPEG-4 Visual / ASP, usually encoded by DivX or Xvid codecs) inside; they are often used for DVD-rips. Such AVI video files often contain "packed B-frames", which is not an optimal frame storage way, but just a workaround for the VfW (Video for Windows) framework shortcomings (i. e., bugs).
To ensure you have a "bad-style" MPEG-4 AVI file, you can check it with a media analyzer utility like MediaInfo (in this case, it'll show you something like "Muxing mode : Packed bitstream").
Fortunately, that wrong thing is easy to "unpack" with an up-to date version of FFmpeg (v2.7+):

$ ffmpeg -i in_bad.avi -codec copy -bsf:v mpeg4_unpack_bframes out_good.avi

The conversion is lossless (neither video nor audio quality is harmed; the file should remain compatible with the hardware players... or even become more compatible), but often can even reduce the resulting AVI container size.

BTW, after "bitstream unpacking", the MPEG-4 video stream becomes standards-compliant, so you can put it directly into the popular MP4 container without transcoding (but it requires the audio stream to be MP4-compatible too, e. g. MP3 is OK);
e. g., here are ~~2.5~~ 3 remuxing examples using the same FFmpeg:

$ ffmpeg -i in10_good.avi -codec copy out10_good.mp4
$ ffmpeg -i in20_bad.avi -codec copy -bsf:v mpeg4_unpack_bframes out20_better.mp4
$ ffmpeg -i in20_bad.avi -codec copy -bsf:v mpeg4_unpack_bframes -movflags faststart out25_best.mp4

You can download the source code and binary builds of the current FFmpeg (for MS Windows, Apple Mac OS X and Linux) freely from the official site.
Usually, you will find a compatible version in the repositories of your favorite Linux distribution;
however, in Debian, it's available only starting from the release 9 "Stretch" (and fortunately, it's currently in the backports for 8 "Jessie" too; and for use in Ubuntu, you need release 15.10 "Wily Werewolf", at least):

# sudo apt-get install ffmpeg

References:

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Last updated: 2017-12-28

2013-03-10

HOWTO: losslessly convert FLV video to MP4 in Linux (Debian)

Well, let's imagine we have a Flash Video (FLV/F4V) container file (possibly "unseekable" or with other minor problems) containing MPEG-4 AVC video & AAC (or MP3) audio.

We'll convert ("remux") it to MP4 without any transcoding (re-encoding), so it'll be very fast, and using only the free tools (available in the official Debian GNU/Linux repositories).

Note: unfortunately, old FLV videos containing VP6 and Sorenson video formats can't be remuxed into MP4 format; if you don't want re-encoding, you can try to remux them into MKV (Matroska); if you just want to fix the seek problems, you can just try FLV-to-FLV remuxing.

Method #1 (recommended): use ffmpeg (it's the main utility from the FFmpeg project).
Install the "ffmpeg" package:
```
# apt-get install ffmpeg
```
Convert a FLV file to MP4, preserving audio & video:
```
$ ffmpeg -i input.flv -codec copy output.mp4
```
And even optimizing it for faster loading:
```
$ ffmpeg -i input.flv -codec copy -movflags faststart output_optim.mp4
```
To extract audio only:
```
$ ffmpeg -i input.flv -codec copy -vn output_a.mp4
```
To extract video only:
```
$ ffmpeg -i input.flv -codec copy -an output_v.mp4
```
Note: you can also use M4A (audio) / M4V (video) file extensions for output, if you like those Apple formats.
Method #2 (alternative): using avconv (it's a part of Libav project, a fork of FFmpeg).
Install the "libav-tools" package:
```
# apt-get install libav-tools
```
Convert a FLV file to MP4, preserving audio & video:
```
$ avconv -i input.flv -codec copy output.mp4
```
To extract audio only:
```
$ avconv -i input.flv -codec copy -vn output_a.mp4
```
To extract video only:
```
$ avconv -i input.flv -codec copy -an output_v.mp4
```

Method #3 (a somewhat ugly one): using MEncoder (a part of the MPlayer project).
Install MEncoder:

# apt-get install mencoder

Convert a FLV file to MP4:

$ mencoder input.flv -ovc copy -oac copy -of lavf -o output.mp4

Note: according to the warning from MEncoder itself, output file can be corrupt:

** MUXER_LAVF *****************************************************************
REMEMBER: MEncoder's libavformat muxing is presently broken and can generate
INCORRECT files in the presence of B-frames. Moreover, due to bugs MPlayer
will play these INCORRECT files as if nothing were wrong!
*******************************************************************************

So probably it suggests that you should better try the MEncoder's favorite AVI format:

$ mencoder input.flv -ovc copy -oac copy -o output.avi

(But that's not what we want here, right?)

Source software packages availability for Debian releases:

ffmpeg: up to Debian 6 "Squeeze", and then again from 9 "Stretch" (also in 8 "Jessie" backports);
libav: starting from 7 "Wheezy" (also in 6 "Squeeze" backports), up to 8 "Jessie";
mplayer: up to 7 "Wheezy", and then from 9 "Stretch".

And yes, it should work for Ubuntu too; any current FFmpeg version should also work in other GNU/Linux or *BSD distros, MS Windows, Apple Mac OS X etc.

References:

ffmpeg Documentation
Libav documentation : avconv
6.1. Selecting codecs and container formats - Chapter 6. Basic usage of MEncoder (MPlayer - The Movie Player documentation)
Wikipedia:

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Last updated: 2017-12-28