My source has the following audio: pcm_bluray, rate=48000Hz, bitrate=2304000 English (BD LPCM) (2.0 ch)
If the source bitrate is 230 kbps, then, can I encode to stereo (using AAC) at a higher bitrate than 160, for playback on A4 devices?
Another source has the following: DCA, rate=48000Hz, bitrate=1536000 English (DTS) (5.1 ch)
If the source bitrate is 154 kbps, then, what is the highest bitrate I can encode to DPL II (using AAC) -- again for A4 devices. The default is 160.
Thanks.
Audio bitrate advice for A4 devices
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Re: Audio bitrate advice for A4 devices
You're off by an order of magnitude on your source bitrates... Your stereo PCM source is 2.304 Mbps and your DTS 5.1 mix is 1.536 Mbps.
Rather than concentrating on the source bitrate to determine your ideal output bitrate, it's better to consider maximums based on the number of channels and the encoder in use. For stereo AAC (including DPL II) encoded using Apple's Core Audio encoder, 192 Kbps is my limit for most tracks.
The absolute limit for stereo AAC on A4 based devices is 320 Kbps.
Rather than concentrating on the source bitrate to determine your ideal output bitrate, it's better to consider maximums based on the number of channels and the encoder in use. For stereo AAC (including DPL II) encoded using Apple's Core Audio encoder, 192 Kbps is my limit for most tracks.
The absolute limit for stereo AAC on A4 based devices is 320 Kbps.
Re: Audio bitrate advice for A4 devices
Thank you. Your response is helpful — I have a lot to learn — but I don't understand *why* you prefer to limit stereo AAC (and DPL II) to 192 Kbps. If you could briefly explain, I'd appreciate it.
And just to be sure I understand, by limit do you mean ceiling? Or do you mean 192 is the floor? If you mean 192 is the floor and 320 is the ceiling, I still wonder if I should encode at 192, 224, 256, ... and why.
Also — if 192 Kbps is an upper limit, the preset default makes sense; but if 192 is the lower limit, why is the default 160 Kbps? Sorry if my ignorance here is painful.
I should mention, I'm more concerned with quality than file size — though does audio bitrate significantly impact file size?
And just to be sure I understand, by limit do you mean ceiling? Or do you mean 192 is the floor? If you mean 192 is the floor and 320 is the ceiling, I still wonder if I should encode at 192, 224, 256, ... and why.
Also — if 192 Kbps is an upper limit, the preset default makes sense; but if 192 is the lower limit, why is the default 160 Kbps? Sorry if my ignorance here is painful.
I should mention, I'm more concerned with quality than file size — though does audio bitrate significantly impact file size?
Re: Audio bitrate advice for A4 devices
If it were me, I would encode the stereo PCM track using CoreAudio AAC at 320kbps (for iPhone/iPad playback). Further, I would convert the DTS track to AC3 at 640kbps (for AppleTV playback). I'm not too concerned with file size, and keeping as much of the audio quality as possible is a high priority.
If the stereo source would have been AC3, I'd likely use something between 160kbps and 256kbps, trending towards the lower number.
If the stereo source would have been AC3, I'd likely use something between 160kbps and 256kbps, trending towards the lower number.
Re: Audio bitrate advice for A4 devices
Thanks so much for this. I think I'm understanding your advice perfectly. And perhaps the reason 160 Kbps is the default is to control for file size?
The only question I have is about your last point. The reason you'd trend lower if the stereo source had been AC3 is because the codec is lossy? I might have thought this would be a reason to trend higher. For example, in another thread, Rodeo suggests to use a higher bitrate because "HandBrake's AC3 encoder isn't really top-notch, and AC3 isn't a particularly efficient codec either."
The only question I have is about your last point. The reason you'd trend lower if the stereo source had been AC3 is because the codec is lossy? I might have thought this would be a reason to trend higher. For example, in another thread, Rodeo suggests to use a higher bitrate because "HandBrake's AC3 encoder isn't really top-notch, and AC3 isn't a particularly efficient codec either."