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Topic: Encoding vs. Transcoding (Read 11801 times) previous topic - next topic
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Encoding vs. Transcoding

What's the difference between encoding a file and transcoding a file?  The only thing I'm able to deduce from some searches I've done is that encoding a file is going from a lossless format (e.g. WAV) to a lossy format (e.g. MP3), whereas transcoding a file is going from one lossy format to another (e.g. MP3 at one bitrate to MP3 of another bitrate).  TIA.

Encoding vs. Transcoding

Reply #1 –
I would say encoding is going from uncompressed to compressed (ie wav or cd to compressed [losless or lossy]), and transcoding is going from compressed to compressed.

Encoding vs. Transcoding

Reply #2 –
Yes (to the original poster beowulf7), encoding refers to encoding from the original. If you have lossless backup this is the same as original. If you have the music in a lossy format then transcoding refers to reencoding (usually between two different codecs) and incurring additional loss during this process.

@hyper84: lossless encoding also compresses the file.
The object of mankind lies in its highest individuals.
One must have chaos in oneself to be able to give birth to a dancing star.

Encoding vs. Transcoding

Reply #3 –
Technically speaking does transcode have to infer a lossy process? I know that's how the term has been adopted but I'm not so sure that is the case. 
daefeatures.co.uk
 

Encoding vs. Transcoding

Reply #4 –
I guess in an etymological sense you're right: trans+code would mean coding into one format from another (without reference to any lossless or lossy). But this is not how it's used here IMO.
The object of mankind lies in its highest individuals.
One must have chaos in oneself to be able to give birth to a dancing star.

Encoding vs. Transcoding

Reply #5 –
When I use the terms, I give them the following meanings:
a) encode: using an encoder to produce a compressed file
b) reencode: using the compressed file as input to the same encoder to produce another compressed file (same format)
c) transcode: using the compressed file as input to another encoder to produce another compressed file (new format)

Don't know if this is how everybody here understands my gibberish, though...

Encoding vs. Transcoding

Reply #6 –
Well from a Signal Processing point of view... even WAV files are encoded, as it represents the analog signal in a digital form

Well anyways, here's the definitions as I understand them:

Waveform data is RAW data, a.k.a. RAW SAMPLES.

ENCODING means representing data in a non-RAW form, usually compressed, although this is optional.

TRANSCODING means converting data representation between one encoding method to a different method (i.e. FLAC to MP3, or MP3 to Vorbis, FLAC to APE, etc.)

CONVERTING... now this is difficult. But from the threads I take it as using the same encoding method but at different settings, e.g. 320 CBR MP3 to VBR MP3, -q6 Vorbis to -q4 Vorbis, etc.

Encoding vs. Transcoding

Reply #8 –
Quote
Transcoding is almost always slower than direct encoding from the original source, if you do not count the ripping process in the encoding.

(the process you refer to as transcoding is actually peeling)
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I googled to find information about peeling, but it only seems to be related to .ogg files and according to wikipedia: "Ogg Vorbis bitrate peeling exists only as a concept as there is not yet an encoder capable of producing peelable datastreams " Also they compare it to Real Media's Surestream, but it seems to be a completely different technology.

I can understand that you can call reducing the bitrate of a clip peeling, but the "transcoding" method I mean can also convert between different formats without the need to re-encode. I have never tried it myself, but I have read that there are programs that can convert an mpeg-encoded file to other formats used in portable players by using what I was calling transcoding. I don't know if the term is right or if it is called something else.

Encoding vs. Transcoding

Reply #9 –
Can you give a link to an application which can convert from one lossy video format to another one without the need to recompress (resulting in additional loss)? I think you may be mixing it up with "de-muxing streams and then muxing them to a different *container*". This however has NOTHING to do with transcoding.

As far as i know, the video-situation is the same as the audio-only situation: lossy->lossy = additional loss and full recompression needed.

-----

Regarding the original question: transcoding is a quite ambigious term. I believe its real meaning is converting from one encoded file to another one in general... so, regardless of if the source is lossy or lossless. However, on ha.org it has been used with the meaning "lossy->lossy" most of the time.

"Re-encoding" on the other hand as well is ambigious, but less - it is used almost always with the meaning "lossy->lossy"... especially when the source and target format is the same.
I am arrogant and I can afford it because I deliver.

Encoding vs. Transcoding

Reply #10 –
Quote
Can you give a link to an application which can convert from one lossy video format to another one without the need to recompress (resulting in additional loss)? I think you may be mixing it up with "de-muxing streams and then muxing them to a different *container*". This however has NOTHING to do with transcoding.

As far as i know, the video-situation is the same as the audio-only situation: lossy->lossy = additional loss and full recompression needed.

-----

Regarding the original question: transcoding is a quite ambigious term. I believe its real meaning is converting from one encoded file to another one in general... so, regardless of if the source is lossy or lossless. However, on ha.org it has been used with the meaning "lossy->lossy" most of the time.

"Re-encoding" on the other hand as well is ambigious, but less - it is used almost always with the meaning "lossy->lossy"... especially when the source and target format is the same.
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Here is a link that mentions converting between different formats without full re-compression. They call it "Compressed Domain Transcoding "

[a href="http://portal.acm.org/citation.cfm?id=852312&dl=ACM&coll=portal]http://portal.acm.org/citation.cfm?id=8523...ACM&coll=portal[/url]

And here is a more in depth description. Taken from this site: "Transcoding differs from the encoding and decoding processes in that both the input and output of the transcoder are MPEG video streams"

http://www.hpl.hp.com/personal/Susie_Wee/P...97/hpidc97.html

Encoding vs. Transcoding

Reply #11 –
If i understand those papers correctly, then what they do is plain simple re-encoding, but with the difference that the video stream doesn't need to be decoded before re-enconding.

Thus, the quality-loss is the same as with lossy->decoding->encoding->lossy ....... it's just faster, and thats it?
I am arrogant and I can afford it because I deliver.

Encoding vs. Transcoding

Reply #12 –
Quote
If i understand those papers correctly, then what they do is plain simple re-encoding, but with the difference that the video stream doesn't need to be decoded before re-enconding.

Thus, the quality-loss is the same as with lossy->decoding->encoding->lossy ....... it's just faster, and thats it?
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As I understand it, the video is not fully re-encoded. The decoding doesn't take up much time compared to encoding so if the benefit was only that you don't have to decode, it wouldn't be much faster. The transcoder uses the facts that it has already been encoded to mpeg and since all mpeg codecs like mpeg1, mpeg2 and mpeg4 have very much in common it doesn't have to fully decode and encode when converting between two formats. The benefit is speed, but I think the quality is actually worse than when you do a full re-encode.

Encoding vs. Transcoding

Reply #13 –
I realize this post is a couple years old, but I was asked a question today, and this specific post was mentioned in the course of the conversation. This post still comes up on Google searches, even if it's "old" by forum standards (Google can be blind to age).

Quote from: a_aa on
I'm not entirely happy with Wikis use of the term "re-encode" when "transcode" is explained...  http://en.wikipedia.org/wiki/Transcode

Nor should you be! The terms are definitely not interchangeable. Technically, a re-encode can be a transcode, but not all transcodes are re-encodes. Don't you just love loosely-defined tech jargon?

Quote from: kalle on
Here is a link that mentions converting between different formats without full re-compression. They call it "Compressed Domain Transcoding " And here is a more in depth description. Taken from this site: "Transcoding differs from the encoding and decoding processes in that both the input and output of the transcoder are MPEG video streams" http://www.hpl.hp.com/personal/Susie_Wee/P...97/hpidc97.html

"Compressed Domain Transcoding" is a very narrowly defined type of transcode that is not synonymous with "re-encode".
The link to that paper is now dead. I've archived it here: http://www.digitalFAQ.com/forum/showthread...video-2177.html

Quote from: kalle on
As I understand it, the video is not fully re-encoded........The benefit is speed, but I think the quality is actually worse than when you do a full re-encode.

Correct on both counts. It is not decoded, not re-encoded, fast, but lossy. Depending on the source, VERY lossy.

Hopefully my 2010 input will clarify any confusion members or Google drive-by's have on this topic. 
Thanks.

Encoding vs. Transcoding

Reply #14 –
The difference between "encoding" and "transcoding" is the same as the difference between "transmitter" and "transceiver".