Refactor AnnexB bitstream conversion for AVC/H.264

Refactor AnnexB bitstream conversion for AVC/H.264

Having an explicit bitstream converter interface will allow us to move
AnnexB conversion code (PrepareAVCBuffer) from mp4_stream_parser.cc into
avc.cc, resulting in cleaner separation of generic mp4 parser code and
codec-specific parts. Which has two advantages:
1. It will simplify HEVC integration by removing HEVC specific code from
public interfaces and might eventually allow us to toggle HEVC with a
local gyp/gn flag and get rid of the global define that has caused a lot
of contention in the current version of HEVC CL.
2. After some additional work we should be able to unify AnnexB
bitstream conversion code, which is currently duplicated between MSE and
FFmpeg code paths (see crbug.com/455379).

BUG=455379
Committed: https://crrev.com/b199d3440e7b516c98cae679e779af9f5670ef44
Cr-Commit-Position: refs/heads/master@{#343818}

[servolk, 2015-08-14 00:37:44]

servolk@chromium.org changed reviewers:
+ ddorwin@chromium.org, sandersd@chromium.org

[ddorwin, 2015-08-14 03:36:47]

ddorwin@chromium.org changed reviewers:
- ddorwin@chromium.org

[ddorwin, 2015-08-14 03:36:47]

ddorwin@chromium.org changed required reviewers:
+ sandersd@chromium.org

[sandersd (OOO until July 31), 2015-08-17 18:24:07]

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/avc.h
File media/formats/mp4/avc.h (right):

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/avc.h...
media/formats/mp4/avc.h:62: class AVCBitstreamConverter : public
BitstreamConverter {
Comment exact what this converts to/from.

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/bitst...
File media/formats/mp4/bitstream_converter.h (right):

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/bitst...
media/formats/mp4/bitstream_converter.h:22: virtual bool
ConvertFrame(std::vector<uint8>* frame_buf,
Comment what these parameters are. (In particular, how output is returned and
where to go to understand subsamples.)

[servolk, 2015-08-17 22:06:24]

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/avc.h
File media/formats/mp4/avc.h (right):

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/avc.h...
media/formats/mp4/avc.h:62: class AVCBitstreamConverter : public
BitstreamConverter {
On 2015/08/17 18:24:07, sandersd wrote:
> Comment exact what this converts to/from.

Done.

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/bitst...
File media/formats/mp4/bitstream_converter.h (right):

https://codereview.chromium.org/1289923003/diff/40001/media/formats/mp4/bitst...
media/formats/mp4/bitstream_converter.h:22: virtual bool
ConvertFrame(std::vector<uint8>* frame_buf,
On 2015/08/17 18:24:07, sandersd wrote:
> Comment what these parameters are. (In particular, how output is returned and
> where to go to understand subsamples.)

Done.

[sandersd (OOO until July 31), 2015-08-17 22:15:35]

lgtm

[servolk, 2015-08-17 22:17:03]

The CQ bit was checked by servolk@chromium.org

[commit-bot: I haz the power, 2015-08-17 22:17:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1289923003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1289923003/60001

[commit-bot: I haz the power, 2015-08-18 00:57:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-18 00:58:00]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[servolk, 2015-08-18 01:10:13]

The CQ bit was checked by servolk@chromium.org

[commit-bot: I haz the power, 2015-08-18 01:11:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1289923003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1289923003/60001

[commit-bot: I haz the power, 2015-08-18 05:20:29]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-08-18 05:21:19]

Patchset 4 (id:??) landed as
https://crrev.com/b199d3440e7b516c98cae679e779af9f5670ef44
Cr-Commit-Position: refs/heads/master@{#343818}