What format should I use for uploading Podcast Files?
Since we already transcode the file you give us into various formats and quality levels (see this article) you need not worry about this one too much. In short "Any standard, high quality audio file should work".
In more detail: We accept various file formats as input: WAV, FLAC, MP3, MP2, Ogg Vorbis, AAC, Windows Media
Note that these file types are identified only by their extension and must match the audio codec contained in the file! (.wav, .flac, .mp3, .mp2, .ogg, .oga, .mp4, .m4a, .wma respectively)
What is the recommended upload format and quality ?
As already mentioned our platform published all episodes in multiple quality levels. (See this article.)
Ideally use a high-quality input file but strike a balance between quality and file-size by compressing it first using a (good) compression codec.
For podcast content (voice with mixed in sounds) we recommend uploading 44.1kHz or 48kHz files compressed with AAC at 160kbps bitrate. At this compression level the quality is nearly transparent to uncompressed originals, even for music content. For uploading in MP3 format we recommend using 192kbps compression.
We strongly recommend against using WAV as an upload format due to it's massive size.