<p><strong>First reason:</strong><br>
Videos / audios in <code>AVI</code> or <code>MKV</code> containers may be encoded by <em>various</em> codecs, and not all them are supported by <code>MP4</code> containters.</p>

<p><strong>Second reason:</strong><br>
Containers are more than <em>simple boxes for videos, audios, subtitles, etc.</em> with some <em>not so important metadata</em> as author or date/time. They have a <em>lot of unevitable valuable information</em>, e. g. the synchronization between audio and video is possible <em>only due to it</em>.</p>

<p>So there is not a reliable algorithm to convert any <code>AVI</code> -> <code>MP4</code> or any <code>MKV</code> -> <code>MP4</code> (and, generally speaking, from one type of container to a different one) <em>without changing the streams</em> (audios, videos, etc.) contained in them - the result may be similar to the one you described.</p>

CC BY-SA 3.0
2017-06-02T18:48:11.397Z
ah! thank you for that explanation. i got an app called "MediaInfo" (on Mac) & after looking at some video's, i see the differences in the MKV's that the MKV2MP4 app can simply change the container on vs the ones it cannot. and i haven't found any AVI's that have any innards that can be used in an MP4. so i guess i can't just have a global batch tool, i'm gonna have to look at each video & make a decision on which utility to use on it. that's a bummer for speed. i wish i could find a handy easy chart that shows which codecs & containers are compatible etc. anyways, thanks!
SyberKnight
CC BY-SA 3.0
2017-05-27T00:47:27.110Z
2017-05-27T01:10:50.423Z
2017-05-27T01:10:50.423Z
MarianD
<p>Faster than converting and possibly ending up with a file that has problems is to install another player like VLC or KMPlayer, etc.</p>

<p><a href="https://itunes.apple.com/us/app/kmplayer/id835776444?mt=8" rel="nofollow noreferrer">https://itunes.apple.com/us/app/kmplayer/id835776444?mt=8</a></p>

<p>VLC is great on PC Desktop but on Android and iOS it's a bit buggy. There are a few 3rd Party Players for iOS that also claim to play everything.</p>

CC BY-SA 3.0
2017-06-02T18:49:57.773Z
i need mp4's to play on Apple TV & iOS. as far as i'm aware, there's no VLC type options for those. my post isn't about players but thanks for your time anyways.
SyberKnight
CC BY-SA 3.0
2017-06-02T05:40:55.160Z
2017-06-02T05:40:55.160Z
Rob
<p>It is worth mentioning that you don't always have to 'convert/transcode' the file (as you have mentioned), in order to change the wrapper. There is an operation called re-wrap, which re-packages the media from one wrapper to another. This isn't the same as the 'fast container switching' that you have described, as re-wrapping works reliably and is often used in broadcast workflows.</p>

<p>For example, <a href="https://evs.com/en/download-area-version/3195" rel="nofollow noreferrer">XSquare/XTAccess</a> software allows you to re-wrap media without a licence. If you refer to the <a href="https://evs.com/en/download-area-version/3195/resource/8969" rel="nofollow noreferrer">list of supported codecs</a>, you will see what re-wraps are possible.</p>

CC BY-SA 3.0
2017-06-29T04:58:05.060Z
*This isn't the same as the 'fast container switching'* - what's the difference?
Gyan
CC BY-SA 3.0
2017-06-29T12:19:22.983Z
@Mulvya - it isn't the same because you don't get the negative side effects mentioned by the author of the question (no audio out of sync, missing audio or glitchy video). Why exactly is a good question - XTAccess is not GPL, unlike the other piece of software so my statement is based on empirical evidence, not theoretical.
Tony Sepia
CC BY-SA 3.0
2017-06-29T12:29:05.667Z
Ok, so XTAccess, as per you, does better remuxing. But they refer to the same process.
Gyan
CC BY-SA 3.0
2017-06-29T01:15:57.907Z
2017-06-29T01:15:57.907Z
Tony Sepia
<p>Why does it seem to be so difficult to simply change a video's container? </p>

<p>For example, when I download ".avi" &amp; ".mkv" video's from the internet &amp; want to watch them on my Apple devices (iPhone, iPad, Apple TV), I need them to be ".mp4" instead. </p>

<p>I don't want to spend the time to go through the whole "conversion/transcoding" process with apps like <strong>Handbrake</strong> when it seems you can simply change their containers out with apps like <strong>Mkv2Mp4</strong> or the old <strong>Video Container Switcher</strong> apps <em>in a fraction of the time</em>. </p>

<p>Problem is, when I use those container changing utilities, various problems arise, like...</p>

<ul>
<li>having mp4's with audio out of sync, or</li>
<li>having mp4's with no audio at all, or</li>
<li>having mp4's with very jittery video. </li>
</ul>

<p>I love the speed of these container changing apps but why don't the video's play exactly the same since they're not actually converting the codecs &amp; such?</p>

<mp4>
Converting Container Problems
SyberKnight
# Converting Container Problems

(Asked by: username_0 on 2017-05-27)

Why does it seem to be so difficult to simply change a video's container?

For example, when I download ".avi" & ".mkv" video's from the internet & want to watch them on my Apple devices (iPhone, iPad, Apple TV), I need them to be ".mp4" instead.

I don't want to spend the time to go through the whole "conversion/transcoding" process with apps like **Handbrake** when it seems you can simply change their containers out with apps like **Mkv2Mp4** or the old **Video Container Switcher** apps *in a fraction of the time*.

Problem is, when I use those container changing utilities, various problems arise, like...

* having mp4's with audio out of sync, or
* having mp4's with no audio at all, or
* having mp4's with very jittery video.

I love the speed of these container changing apps but why don't the video's play exactly the same since they're not actually converting the codecs & such?

**Tags:** mp4


---

## 3 answers

### Answer by username_1 on 2017-05-27. Score: 0 | Accepted answer

**First reason:**  
Videos / audios in `AVI` or `MKV` containers may be encoded by *various* codecs, and not all them are supported by `MP4` containters.

**Second reason:**  
Containers are more than *simple boxes for videos, audios, subtitles, etc.* with some *not so important metadata* as author or date/time. They have a *lot of unevitable valuable information*, e. g. the synchronization between audio and video is possible *only due to it*.

So there is not a reliable algorithm to convert any `AVI` -> `MP4` or any `MKV` -> `MP4` (and, generally speaking, from one type of container to a different one) *without changing the streams* (audios, videos, etc.) contained in them - the result may be similar to the one you described.

> **Comments:**
> **username_0**: ah! thank you for that explanation. i got an app called "MediaInfo" (on Mac) & after looking at some video's, i see the differences in the MKV's that the MKV2MP4 app can simply change the container on vs the ones it cannot. and i haven't found any AVI's that have any innards that can be used in an MP4. so i guess i can't just have a global batch tool, i'm gonna have to look at each video & make a decision on which utility to use on it. that's a bummer for speed. i wish i could find a handy easy chart that shows which codecs & containers are compatible etc. anyways, thanks!  

---

### Answer by username_2 on 2017-06-02. Score: 0

Faster than converting and possibly ending up with a file that has problems is to install another player like VLC or KMPlayer, etc.

<https://itunes.apple.com/us/app/kmplayer/id835776444?mt=8>

VLC is great on PC Desktop but on Android and iOS it's a bit buggy. There are a few 3rd Party Players for iOS that also claim to play everything.

> **Comments:**
> **username_0**: i need mp4's to play on Apple TV & iOS. as far as i'm aware, there's no VLC type options for those. my post isn't about players but thanks for your time anyways.  

---

### Answer by username_3 on 2017-06-29. Score: 0

It is worth mentioning that you don't always have to 'convert/transcode' the file (as you have mentioned), in order to change the wrapper. There is an operation called re-wrap, which re-packages the media from one wrapper to another. This isn't the same as the 'fast container switching' that you have described, as re-wrapping works reliably and is often used in broadcast workflows.

For example, [XSquare/XTAccess](https://evs.com/en/download-area-version/3195) software allows you to re-wrap media without a licence. If you refer to the [list of supported codecs](https://evs.com/en/download-area-version/3195/resource/8969), you will see what re-wraps are possible.

> **Comments:**
> **username_4**: *This isn't the same as the 'fast container switching'* - what's the difference?  
> **username_3**: @Mulvya - it isn't the same because you don't get the negative side effects mentioned by the author of the question (no audio out of sync, missing audio or glitchy video). Why exactly is a good question - XTAccess is not GPL, unlike the other piece of software so my statement is based on empirical evidence, not theoretical.  
> **username_4**: Ok, so XTAccess, as per you, does better remuxing. But they refer to the same process.  

---

