On Tue Apr 12 Simon Nash wrote: >> dinkypumpkin wrote: >> >> When mp4tags rewrites the MP4 metadata on save, the underlying MP4 >> library does the arithmetic to calculate the necessary values and >> fill in the esds atom. From perusing the ffmpeg code, it looks like >> the required logic could be added, but I'm not sure it should be. I >> don't think zero is an incorrect value for those fields, plus it >> would sort of violate the codec-based model of ffmpeg. > > This makes sense, but it doesn't explain why ffmpeg sets the > maxBitrate field. Where does it get the value from?
In order to understand the analysis of the metadata, below are extracts for the files tested with the Marantz player. Bells1_noscript.m4a is the only file that doesn't play. The average bitrate is zero. The average bitrate in all the other files is non zero. test1.mp4 does not play (as the Marantz does not recognise a .mp4 file), but change the extension to .m4a and it plays OK. Bells1_noscript.m4a is downloaded with get_iplayer. Bells1_script.m4a is the same file fixed up with Jon's script. Simon can explain what the other files are. Bells1_noscript.m4a type ftyp majorBrand = M4A type esds decConfigDescr bufferSizeDB = 0 (0x000000) <24 bits> maxBitrate = 143325 (0x00022fdd) avgBitrate = 0 (0x00000000) Bells1_script.m4a type esds decConfigDescr bufferSizeDB = 620 (0x00026c) <24 bits> maxBitrate = 135328 (0x000210a0) avgBitrate = 128002 (0x0001f402) Bells1_noscript_bitrate.m4a type esds decConfigDescr bufferSizeDB = 0 (0x000000) <24 bits> maxBitrate = 143325 (0x00022fdd) avgBitrate = 128002 (0x0001f402) Bells1_noscript_bitrate_buffer.m4a type esds decConfigDescr bufferSizeDB = 620 (0x00026c) <24 bits> maxBitrate = 143325 (0x00022fdd) avgBitrate = 128002 (0x0001f402) test1.mp4 type ftyp majorBrand = mp42 type esds decConfigDescr bufferSizeDB = 1164 (0x00048c) <24 bits> maxBitrate = 329224 (0x00050608) avgBitrate = 320110 (0x0004e26e) test1a.m4a type ftyp majorBrand = M4A type esds decConfigDescr bufferSizeDB = 1164 (0x00048c) <24 bits> maxBitrate = 329224 (0x00050608) avgBitrate = 320110 (0x0004e26e) _______________________________________________ get_iplayer mailing list [email protected] http://lists.infradead.org/mailman/listinfo/get_iplayer
