how to improve the quality of resultant video when merging audio-video with ffmpeg?

When merging an audio and video with ffmpeg, the quality of the resultant video goes down. How to we improve the quality(esp. the audio quality)?

The audio quality gets degraded to quite an extent with random screeches in between. I've tried converting the audio to mp3 and video to mp4 before merging them, tried various audio-video parameters li开发者_JS百科ke bitrate, sample-rate, qscale etc but still unsuccessful. Any help would be greatly appreciated!

The -acodec copy command line option should just copy the audio stream and not re-encode it. For the video stream -vcodec copy. Also, you can used the -sameq option for the video stream.

See this answer for a little more detail.

i try using the -sameq, yeah it gives a good quality of the video but what I notice was the file size increases.

Using -q:v 1 applies the best possible resolution. Number between 1 and 35. One is the best quality.