Use the `-y` option to automatically overwrite [[docs](https://ffmpeg.org/ffmpeg.html#Main-options)]:

    ffmpeg -y -i input.flac output.mp3



I need to add the `-y` global switch before specifying the output file to accomplish this 

    ffmpeg -i /audio/191079007530_1_01.flac -t 51 -ss 69 -y /clips/44z274v23303t264y2z2s2s2746454t234_clip.mp3 2&gt;&amp;1 &gt;&gt; /ffmpegLogs.log

&gt; Alternatively, you can use the `-n` option to deny overriding the
&gt; file.

If there&#39;s someone using the [ffmpeg-python](https://github.com/kkroening/ffmpeg-python) wrapper, then you can use `overwrite_output` arg when running the stream.

```python
stream = ffmpeg.input(&#39;dummy.mp4&#39;)
stream = ffmpeg.filter(stream, &#39;fps&#39;, fps=25, round=&#39;up&#39;)
stream = ffmpeg.output(stream, &#39;dummy2.mp4&#39;)
ffmpeg.run(stream, overwrite_output=True)
```

I want to check my environment for the existence of a variable, say `&quot;FOO&quot;`, in Python. For this purpose, I am using the `os` standard library. After reading the library&#39;s documentation, I have figured out 2 ways to achieve my goal:

Method 1:  

    if &quot;FOO&quot; in os.environ:
        pass


Method 2:

    if os.getenv(&quot;FOO&quot;) is not None:
        pass


I would like to know which method, if either, is a good/preferred conditional and why.


What is a good practice to check if an environmental variable exists or not?

I am working on a nested flexbox layout which should work as follows:

The outermost level (`ul#main`) is a horizontal list that must expand to the right when more items are added to it. If it grows too big, there should be a horizontal scroll bar.

&lt;!-- language: css --&gt;

    #main {
        display: flex;
        flex-direction: row;
        flex-wrap: nowrap;
        overflow-x: auto;
        /* ...and more... */
    }

Each item of this list (`ul#main&#160;&gt;&#160;li`) has a header (`ul#main&#160;&gt;&#160;li&#160;&gt;&#160;h2`) and an inner list (`ul#main&#160;&gt;&#160;li &gt;&#160;ul.tasks`). This inner list is vertical and should wrap into columns when needed. When wrapping into more columns, its width should increase to make room for more items. This width increase should apply also to the containing item of the outer list.

&lt;!-- language: css --&gt;

    .tasks {
        flex-direction: column;
        flex-wrap: wrap;
        /* ...and more... */
    }

My problem is that the inner lists don&#39;t wrap when the height of the window gets too small. I have tried lots of tampering with all the flex properties, trying to follow the guidelines at [CSS-Tricks][1] meticulously, but no luck.

This [JSFiddle][2] shows what I have so far.

**Expected result** *(what I want)*:

![My desired output](https://i.stack.imgur.com/urybZ.png)

**Actual result** *(what I get)*:

![My current output](https://i.stack.imgur.com/YAVx2.png)

**Older result** *(what I got in 2015)*:

![My older output](https://i.stack.imgur.com/t5SQd.png)

UPDATE
------

After some investigation, this is beginning to look like a bigger issue. **All major browsers behave the same way**, and it has nothing to do with my flexbox design being nested. Even simpler flexbox column layouts refuse to increase the list&#39;s width when the items wrap.

This [other JSFiddle][3] clearly demonstrates the problem. In current versions of Chrome, Firefox and IE11, all items wrap correctly; the list&#39;s height increases in `row` mode, but its width does not increase in `column` mode. Also, there is no immediate reflow of elements at all when changing the height of a `column` mode, but there is in `row` mode.

However, the [official specs *(look specifically at example 5)*][4] seem to indicate that what I want to do should be possible.

Can someone come up with a workaround to this problem?

UPDATE 2
--------

After a lot of experimenting using JavaScript to update the height and width of various elements during resize events, I have come to the conclusion that it is too complex and too much trouble to try to solve it that way. Also, adding JavaScript definitely breaks the flexbox model, which should be kept as clean as possible.

For now, I&#39;m falling back to `overflow-y: auto` instead of `flex-wrap: wrap` so that the inner container scrolls vertically when needed. It is not pretty, but it is one way forward that at least does not break useability too much.


  [1]: https://css-tricks.com/snippets/css/a-guide-to-flexbox/
  [2]: http://jsfiddle.net/4p8fpLms/
  [3]: http://jsfiddle.net/nwccdwLw/1/
  [4]: http://www.w3.org/TR/css-flexbox-1/#flex-flow-property

When flexbox items wrap in column mode, container does not grow its width

I ran:

    ffmpeg -i input.flac output.mp3

This prompts:

&gt; File &#39;output.mp3&#39; already exists. Overwrite? [y/N] y

How do I automatically say &quot;yes&quot;?

ffmpeg overwrite output file if exists

I ran:
<pre><code class="hljs language-css">ffmpeg -i input.flac output.mp3
</code></pre>
This prompts:
> File 'output.mp3' already exists. Overwrite? [y/N] y
How do I automatically say "yes"?

how can i convert a video to images using ffmpeg? Example am having a video with total duration 60 seconds. I want images between different set of duration like between 2-6 seconds, then between 15-24 seconds and so on. Is that possible using ffmpeg?

FFMPEG- Convert video to images

There does not seem to be any explanation online as to what these are. People talk about them a lot. I just want to know what they are and why they are significant. Using -video_track_timescale, how would I determine a number for it? Is it random? Should it be 0?

What is video timescale, timebase, or timestamp in ffmpeg?

I want to use ffmpeg to accelerate video encode and decode with an NVIDIA GPU.
  
From [NVIDIA&#39;s website][1]: 
 
&gt; NVIDIA GPUs contain one or more hardware-based decoder and encoder(s) (separate from the CUDA cores) which provides fully-accelerated hardware-based video decoding and encoding for several popular codecs. With decoding/encoding offloaded, the graphics engine and the CPU are free for other operations.

My question is: can I use CUDA cores to encode and decode video, maybe faster?


  [1]: https://developer.nvidia.com/nvidia-video-codec-sdk

GPU-accelerated video processing with ffmpeg

I am trying to convert a video clip (MP4, yuv420p) from 30 fps to 24 fps. The number of frames is correct so my output should change from 20 minutes at 30fps to 25 minutes at 24fps. Everything else should remain the same.

Try as I might everything I try with ffmpeg converts the frame rate but changes the number of frames to keep the same duration or changes the duration without altering the framerate.

So I have been typically trying things like;

    ffmpeg -y -r 30 -i seeing_noaudio.mp4 -r 24 seeing.mp4

(I&#39;m doing this on windows but normally would be on linux). That converts the framerate but drops frames so the total duration is unaltered.

Or I have tried 

    ffmpeg -y -i seeing_noaudio.mp4 -filter:v &quot;setpts=1.25*PTS&quot; seeing.mp4

Which changes the duration but not the framerate.

Surely I should be able to do this with a single ffmpeg command without having to reencode or even as some people suggested going back to the original raw frames.

Help please


Using ffmpeg to change framerate

I have dockerized an app which has ffmpeg installed in it via libav-tools. The app launches without problem, yet the problem occured when fluent-ffmpeg npm module tried to execute ffmpeg command, which was not found. When I wanted to check the version of the ffmpeg and the linux distro set up in the image, I used `sudo docker exec -it c44f29d30753 &quot;lsb_release -a&quot;` command, but it gave the following error: `OCI runtime exec failed: exec failed: container_linux.go:296: starting container process caused &quot;exec: \&quot;lsb_release -a\&quot;: executable file not found in $PATH&quot;: unknown`

Then I realized that it gives me the same error with all the commands that I try to run inside the image or the container.

    OCI runtime exec failed: exec failed: container_linux.go:296: starting container process caused &quot;exec: \&quot;ffmpeg -a\&quot;: executable file not found in $PATH&quot;: unknown

This is my Dockerfile:

    FROM ubuntu:xenial
    FROM node
    RUN apt-get -y update
    RUN apt-get --yes install libav-tools
    RUN mkdir -p /usr/src/app
    WORKDIR /usr/src/app
    COPY package.json /usr/src/app
    RUN npm install
    COPY . /usr/src/app
    RUN npm run build
    ENV NODE_ENV production
    EXPOSE 8000
    CMD [&quot;npm&quot;, &quot;run&quot;, &quot;start:prod&quot;]

I would kindly ask for your help. Thank you very much!

Content Type	Original Author	Original Content on Stackoverflow
Question	Muhammad Omer Aslam	View Question on Stackoverflow
Solution 1 - Ffmpeg	Veer	View Answer on Stackoverflow
Solution 2 - Ffmpeg	Muhammad Omer Aslam	View Answer on Stackoverflow
Solution 3 - Ffmpeg	leminhnguyen	View Answer on Stackoverflow

ffmpeg overwrite output file if exists

Ffmpeg Problem Overview

Ffmpeg Solutions

Solution 1 - Ffmpeg

Solution 2 - Ffmpeg

Solution 3 - Ffmpeg

When flexbox items wrap in column mode, container does not grow its width

What is a good practice to check if an environmental variable exists or not?

Attributions