Redubbing and re-encoding mp4 files with minimal loss

[techmot]

Hi, I am trying to redub audio of some episodes of a TV show episodes and encode them to an MP4 file in an editing programme like Premiere. The files where from youtube and the file size is only around 250mb, with a video bitrate total of about 715kbps, low yes but quality is surprisingly not too bad considering the low bitrate. Framesize is 626x480, audio bitrate 128kbps. I am redubbing audio that was used originally when the episode was broadcast on TV, simply by cutting the relevant audio track out and replacing it with the new audio. When I encode the file to an MP4 (H.264) , I set the video quality to just above the size of the original file (about 270 and setting it to about 0.5 on the quality scale, the audio I set at 160kbps. Considering that I set the quality a little more than what the original was I would expect there would be little quality loss, but on viewing the outputted file there is some noticeable compression despite the file size being a little more than the original. I have used CBR.

Is there a way of keep the quality as close to the original without the file size being significantly larger than the original file?. Setting the quality scale in Premiere's export settings to something around the 3.0 mark encodes the file to around 1GB.

[poisondeathray]

I am redubbing audio that was used originally when the episode was broadcast on TV, simply by cutting the relevant audio track out and replacing it with the new audio.

Are you making video and/or audio edits in terms of cuts or timing ? e.g. does one version have commericals or other edits you need to match? If not, just swap the audio tracks by stream copying using mp4box or ffmpeg. No quality loss, same filesize . Premiere would be the wrong tool for this task

If you are only making audio edits, export the audio and mux with original video; no video quality loss

If you need to re-encode video, you can use voukoder in premiere and libx264 to get better compression and quality at a given filesize. The bundled h264 encoder with Premiere is not very good

[davexnet]

If you're not changing the video, just multiplex the new audio with the existing video, then you would not incur a quality loss.
Re-encoding any lossy video to a new video with similar settings will always be worse

[techmot]

If you're not changing the video, just multiplex the new audio with the existing video, then you would not incur a quality loss.
Re-encoding any lossy video to a new video with similar settings will always be worse

Basically yes I am just changing the audio by cutting out the original track and replacing it with a new one from a difference source. The DVD versions from youtube use different songs than the TV broadcasts, so I am editing the original songs with the DVD versions so that they match as much as possible to the original broadcasts. The source I use for the versions with the original songs have a channel logo which obviously the DVD versions don't include.

If I just export the audio only to mux does the video need exporting as well?. I'm guessing that would involved encoding though. How to I mux the audio with the video? can this be done in Avidemux?.

[techmot]

I am redubbing audio that was used originally when the episode was broadcast on TV, simply by cutting the relevant audio track out and replacing it with the new audio.

Are you making video and/or audio edits in terms of cuts or timing ? e.g. does one version have commericals or other edits you need to match? If not, just swap the audio tracks by stream copying using mp4box or ffmpeg. No quality loss, same filesize . Premiere would be the wrong tool for this task

If you are only making audio edits, export the audio and mux with original video; no video quality loss

If you need to re-encode video, you can use voukoder in premiere and libx264 to get better compression and quality at a given filesize. The bundled h264 encoder with Premiere is not very good

When exporting the audio only Premiere, does the video need exporting separately as well to mux the files?. I am just editing parts of the audio in each episodes and using the original music (from the TV broadcasts I have recorded which use the original songs). The method I have been using is unlinking the audio and video, using the razor tool and cutting the parts where the song/s are to be removed to replace with the original songs.

[techmot]

Just tried muxing the audio only track with the video by clicking on "audio" in Avidemux and simply replacing the original track with the new audio. Muxed the audio like a treat. Why didn't I do this before lol. Well you learn something new everyday. There are some episodes where on the DVD version some lines have been cut out compared to the TV broadcasts (no idea why but it seems to be the norm for some TV shows when released on video to have scenes and/or dialogue cut out, often in some cases for no apparent reason). Of course that presents a problem where you can't just export the audio and some video re-encoding is needed I would imagine).