Is there a way to turn AVI into MP4 without losing any quality at all?

In practice, no. Lossless conversion is only possible when the codec inside is compatible with the target container, meaning that swapping the container is enough on its own. Codecs found inside AVI files such as DivX, Xvid and MPEG-4 Part 2 do not work reliably with the MP4 container, so the picture has to be re-encoded. The best you can do is choose a bitrate high enough to minimise the loss, not to eliminate it.

If I choose a high bitrate, does the loss disappear completely?

It does not disappear completely, but it can drop below the threshold of perception. At a sufficiently high bitrate H.264 can preserve almost all of the detail in the source; telling them apart by eye becomes very hard. But that has a cost: the file grows, and in some cases can even come out larger than the original. So raising the bitrate indefinitely is not sensible, you need to pick a value proportionate to the quality of the source.

What happens if I convert the same file twice?

The loss accumulates and cannot be undone. Detail thrown away in the first compression does not come back in the second pass, and new detail is discarded on top of it. That is why you should always convert in one go from the most original source. If you have both an AVI and a previously converted MP4, run the new operation on the AVI.

Could I not just keep the AVI as it is instead of converting?

Keeping it for archival purposes is something you should be doing anyway, and it does not conflict with converting. The healthiest approach is to preserve the original and produce an MP4 copy alongside it for daily use. If you stay on AVI alone, your file will not open on most modern devices, meaning you will have an archive that is technically preserved but practically unusable. Keeping two copies removes that dilemma entirely.

Quality Loss in AVI to MP4 Conversion: What Do You Really Lose?

Asking the right question

The answer to "will quality drop if I turn AVI into MP4?" is short: yes, it drops somewhat. But that answer is no use on its own, because the real decision depends on a different question: how much does it drop and what are you getting in return?

This article puts two options side by side: leaving the file as it is in AVI, and converting it to MP4. Both of them have real costs.

First, let us be clear about why there is loss

When converting MKV or MOV files to MP4 there is usually no quality loss, because the H.264 stream inside is copied into the new container without ever being opened up. This is called a remux.

With AVI that route is closed. AVI files typically carry DivX, Xvid or MPEG-4 Part 2. In practice the MP4 container does not house these codecs reliably. As a result the picture has to be opened up and compressed again with H.264 — that is, a genuine re-encode.

Re-encoding is lossy by definition. The codec shrinks the file by throwing away the detail the human eye finds hardest to notice. That detail does not come back.

The cost of staying on AVI

Not converting is not free. If you leave the file as it is, you are accepting the following:

It will not open on most devices. The great majority of smart televisions, phones, tablets and games consoles either do not recognise AVI at all or cannot decode the codec inside it. The fact that it opens on your computer in VLC does not change that.

It cannot be uploaded to the web. Most social media platforms, video services and web forms expect MP4. Some accept AVI and convert it on their side — but then the settings that determine quality are chosen by them, not by you.

It causes trouble in editing programs. Modern editing software can struggle to import AVI, or may not accept it at all.

It takes up more space. AVI-era codecs need far more data than modern codecs to achieve the same visual quality. So you are carrying around an already-large file without getting anything in return.

There is no hardware decoder. Modern devices decode H.264 and H.265 with dedicated circuitry; this is both fast and easy on the battery. Old codecs are decoded on the processor, which on a phone or tablet means more heat and more battery drain.

It becomes even more inaccessible over time. The number of software packages supporting a format does not grow over time, it shrinks.

The cost of moving to MP4

There are real costs on the other side too, and they should not be played down:

Some quality loss. With a good bitrate this loss is usually not noticeable to the naked eye, but technically it is there and it cannot be undone. Where does it show up most? In scenes with motion and detail — crowds, foliage, water, fast camera movement. In a static dialogue scene it is almost impossible to see the difference.

Processing time. Re-encoding is a heavy computation. On a long file it can run for many minutes.

Having to choose settings. A bitrate that is too low creates visible degradation; one that is too high makes the file needlessly large.

Source problems are carried across. Conversion does not fix audio-video drift or corrupted frames that already exist in the source.

Comparison table

| | Staying on AVI | Moving to MP4 | |---|---|---| | Picture quality | Whatever the source is | Some loss | | Device compatibility | Very limited | Almost universal | | File size | Large | Usually shrinks | | Uploading to the web | Problematic | Trouble-free | | Battery and processor load | High | Low, hardware decoding | | Processing time | None | Can take minutes | | Long-term accessibility | Declining | Strong |

The decision section

If you want to watch, share or upload the file somewhere: convert it. The quality of a file that will not open is of no practical use at all. In this scenario the trade clearly favours converting.

If the file is an archive record and you rarely touch it: do both. Keep the original AVI and produce an MP4 copy alongside it. This is the most practical piece of advice in the article, and it removes the need to choose between the two options. Disk space is far cheaper than a loss that cannot be reversed.

If the source is already low quality: do not hesitate to convert. On an old recording that is low resolution and already compressed, the additional loss is barely noticeable, while the compatibility gain is large.

If the source is high quality and will be used in professional work later: definitely preserve the original and choose a generous bitrate for the conversion. If you are going to edit, avoid recompressing at every stage.

If you are going to edit the video again later: editing on the converted MP4 and exporting again stacks the loss on top of itself. Always go back to the most original source.

Our AVI to MP4 converter performs this operation with sensible settings, but whichever decision you make, keeping your original file is in your hands and that is the most valuable protection of all.

In summary

AVI conversion looks like a question of quality, but it is really a question of usability. What you lose is an amount of detail that in most scenarios will go unnoticed; what you gain is a file that opens everywhere.

And the best news is this: it does not have to be an either/or choice. Keeping the original and producing a converted copy alongside it lets you hold on to the advantages of both sides.