mp4 bit rate

[tblake]

Hi guys,

I have been converting few mkv files to mp4(for apple tv) using handbrake and I had a question regarding bit rate.

Does a video bit rate of 895kbps in MKV(FourCC avc1) have similar quality to the same bit rate in MP4(FourCC, V_MPEG4/ISO/AVC)?

The mkv files(BD Rips) are around 950MB, but converting them to MP4 using "Costant Quality(RF=20, Normal preset) ends up having a size of around 1.9GB although the video codecs (given above) used are the same as the bit rate of the MP4 is 1598kbps.

Is there a reason why handbrake is using a higher bit rate than the source with the default setting ? Or is it just that handbrake is not reading the source bit rate when determining the default bit rate.

If there is no specific advantage, I would like to keep the file sizes small. What preset in handbrake should I use to achieve a similar file size with my output MP4 files.

Thanks,
Tony

[jagabo]

Does a video bit rate of 895kbps in MKV(FourCC avc1) have similar quality to the same bit rate in MP4(FourCC, V_MPEG4/ISO/AVC)?

Yes. There is a small difference in overhead between the containers that may one file come out slightly bigger or smaller.

The mkv files(BD Rips) are around 950MB, but converting them to MP4 using "Costant Quality(RF=20, Normal preset) ends up having a size of around 1.9GB although the video codecs (given above) used are the same as the bit rate of the MP4 is 1598kbps.

Is there a reason why handbrake is using a higher bit rate than the source with the default setting ?

Yes, you used a CRF that resulted in a higher bitrate than the original file.

Or is it just that handbrake is not reading the source bit rate when determining the default bit rate.

The encoder doesn't care about the bitrate of the source video. It gets uncompressed frames and encodes them with the quality you specify.

If there is no specific advantage, I would like to keep the file sizes small. What preset in handbrake should I use to achieve a similar file size with my output MP4 files.

If you require specific file sizes use bitrate based encoding rather than quality based encoding.